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NATURE aM CONTROL 
o/' TANNERY PROCESSES 

PUBLISHED BV THE 

Shoe and Leather Reporter 




Copyrighted, 1922, by Joseph R. Lorenz 





UNLESS 



the tanner "works in" the best obtainable 
raw materials, the most perfected tanning 
will be useless. 

Buy your hides and skins only from reliable 
sources able and willing to back up their 
written contracts. 

In dealing with Schmoll Fils 8 Co. you will 
at all times find an organization in a position 
to safe-guard your essential need, namely — 

"Hides and Skins of standard quality 
at origin market prices." 

You can obtain all these advantages, without 
incurring the disadvantage and risk of buy- 
ing from strange people thousands of miles 
away from you, by dealing with us. 



SCHMOLL FILS & CO., Inc. 






Scktol'Hs^CoJnc. 



— SINCE 1836 — 

International Hide Merchants 
Importers of Calf and Goatskins 
Distributors of Tanning Materials 

SCHMOLL-HLS BUILDING 
19-25 SPRUCE ST., NEW YORK 







H 



NATURE AND CONTROL OF TANNERY PROCESSES 

HEMATINE CRYSTALS-i 

also all other 

DYEWOOD PRODUCTS 

of the 

STAMFORD DYEWOOD CO. 
ANILINE COLORS 

FANCY COLORS 

Ooze Gray 
Ooze Brown 
Ooze Black 

New York Color & Chemical Co. 

Manufacturers of ANILINE COLORS 

About May first we move our main office, warehouse, 
laboratories, etc., from 98 John Street, New York City, to 
our New Plant in BELLEVILLE, New Jersey, nine miles 
from New York City. 




Main Office (after May 1st), Belleville, New Jersey 



164 Federal St., Boston, Mass. W. B. Carter, 1123 Columbia Ave., Clucago, lU. 

FACTORIES— BELIEVILLE, N. J.; PHII,.4DE1.PHI.*, PA. 



m \'' >922 



• 

NATURE AND CONTROL OF TANNERY PROCESSES 



Nature and Control 
of Tannery Processes 



A Practical Exposition of the Purposes and Functions of the 
Beamhouse, Chrome Tanning, and Fat Liquoring 
Processes, as Revealed by the Latest Re- 
searches, and of the Means for the 
Economic Control of these 
Processes Within the 
Tannery 



By JOSEPH R. LORENZ 



PRINTED AND PUBLISHED BY THE 

SHOE AND LEATHER REPORTER 

Price $2.00 

(Copyrighted, 1022, by Joseph R. Lorenz) 



NATURE AND CONTROL OF TANNERY PROCESSES 



The STAR Signifies A the SERVICE 




/ 






IMPORTERS EXPORTERS 

HIDES and CALF SKINS 



CALFSKINS 

Dry and Green Salted 

HORSE FRONTS 



Chestnut Extract 
Hemlock Extract 



English — French — German 



HORSEHIDES 

Dry and Salted 
HORSE BUTTS 
TANNING MATERIALS 

Oak Bark 

Solid Quebracho 

Liquid Quebracho 

IMPORTERS —EXPORTERS 

— Russian — Danish — Swedish 

Holland — River Plate and Domestic 



CATTLE HIDES 

Dry and Green Salted 
GOATSKINS 



Mangrove Bark 
Divi Divi, Etc. 



Norwegian 



Finland 



The STAR Signifies the SERVICE 

We prefer to give Service rather than to talk about it. By its actual 

working out in daily transactions, customers become such champions 

of our organization that we frequently wonder if there is anyone in 

the industry who needs to be told of its resultful mechanism. 

Yet we are not satisfied to let our friends do all our promotion for us, 

w^e wish to assert that every pledge they make for us will be exactly 

fulfilled. 

The STAR Symbolizes Service — that STAR never dims because it is 
kept bright by accomplishment. 



JULES STAR & COMPANY 



26-28 Ferry Street, NEW YORK 

130 North WeUs St., CHICAGO 



)G!.A659866 



'■*^^:.h 



M 



l&i 



^ 



NATURE AND CONTROL OF TANNERY PROCESSES 



Author's Preface 



The rapid strides made witliin tlie past live years by all branches of the 
tanning industry, especially by that of chrome tanning, is a matter of knowledge 
to all leather-chemists who follow the work of such of their colleagues as 
Wilson and Thomas in America, and Stiasny, Pahrion. and Alfred Seymour- 
Jones in Europe; these names have, in fact, become as well-known to most 
tannery-chemists of today, as were those of Procter and Wood associated in 
the minds of leather-chemists of a generation ago with the pioneering work 
In the chemistry of tanning with which Procter and Wood are universally 
credited. 

To the investigations of our modern workers may be said to belong the 
distinction of having disclosed to the tanner the real nature of most 
Of the important processes employed today in the manufacture of leather. 
The effect of thirty years or more of effort on the part of the leather- 
chemists, as directed toward the solution of the "mysteries" of tanning, 
has thus been to elevate the art of leather-making from the position of obscurity 
in which it remained throughout the ages, to that of an exact chemical indus- 
try, in which it may safely be said to find itself today. 

This little book is addressed to the practical tanner and manufacturer of 
chrome-tanned upper-leather, as well as to the tannery-chemist. As its title 
indicates, It is an exposition of the purposes and functions of the beamhouse, 
chrome tanning and fat-liquoring proce sses, as revealed by the latest authorita- 
tive researches, and of the means for the chemical control of these processes 
within the tannery. It is so written that anyone having a high-school education, 
or its equivalent, can understand the principles set forth in it. In the subject- 
matter will be found a digest of the principal journal-articles bearing on leather- 
chemistry, as related to chrome-tanning, which have appeared to notice in the 
last fifteen years ; at the close of each of the descriptive chapters on the pro- 
cesses of tanning will be found, in addition, a guide to the analytical control of 
the process described, this having been prepared, to a great extent, from data 
gathered by the author during the term of his own experience of eight years as 
tannery-chemist; finally, in the chapter on "The Fat-Liquoring Process" wUl be 
found the principles of J. R. Blockey's recent book on the "AppUcation of Oils 
and Greases to Leather." 

The author is indebted to Mr. Irving W. Skilton, president of the North- 
eastern Leather Company, tor valuable counsel given in the preparation of this 



treatise. 



J. R. L. 



NATURE AND CONTROL OF TANNERY PROCESSES 



nfiliiiiiiiiiiiiiiiii^ 



:>iiiijLii 



m 



Retanning of Chrome Leather 

During the war the United States Government, as well as the Gov- 
ernments of the Allies, placed orders for large quantities of retanned 
Chrome upper leather. This leather was found essential for 
soldiers* trench shoes, being practically waterproof with excellent 
wearing qualities. 

Do you know that about 90 per cent of this leather was retanned 
with Quebracho? 

That of this about 75 per cent was retanned with Liquid Quebracho 
Extract, and the remainder with Argam (Crown Brand) Solid 
Quebracho Extract. That the bulk of the liquid used was S. M. 
brand of Liquid Extract of Quebracho made "direct from the wood." 

Liquid Quebracho Extract 

S. M. and S. M. S. Brands 

"made direct from the wood" 

are manufactured only at our Brooklyn factory. Greenpoint, New 
York. 

These extracts cannot be imitated by dissolving and 
treating chemically Ordinary Solid Quebracho Extract 

For particulars and information regarding these and other vegetable 
tanning materials, write to 



THE TANNIN CORPORATION 

Main Office: 80 Maiden Lane NEW YORK, N. Y. 



REPRESENTED AT 



TORONTO, CANADA 
13 Wellington St., East 







NATURE AND CONTROL OF TANNERY PROCESSES 



Contents 



SOAKING OF HIDES Page 
Soaking Process, Analytical Control of 9 

FIRST FLESHING 

Chemical Behavior of Acids, Alkalies, and Salts Employed in 

Tanning 11 

THE LIMING PROCESS 

Analytical Control of 15 

DELIMING AND BATING 

Deliming and Bating Process, Analytical Control of 21 

Method of Ascertaining Weight of Dry Substance in Wet Hides,. 23 
Diagram of Sections of Raw Hide Before and After Liming and 

Bating, Respectively 23 

THE PICKLING PROCESS 

Analytical Control of 23 

THE CHROME - TANNING PROCESS 

Analytical Control of 27 

Method for Finding the Capacity of Tannery Paddle-Vats, Tanks 

and Pits 33 

RETANNING OF CHROME LEATHER 35 

"NEUTRALISING" OF CHROME - TANNED LEATHER 

Neutralising Process. Analytical Control of 35 

THE FAT - LIQUORING PROCESS 

Analytical Control of 37 



Copyrighted, 1922, by J. R. Lorenz 



NATURE AND CONTROL OF TANNERY PROCESSES 





COD OIL 



Pure Tanked 

Newfoundland 



Fifty Years' Experience 
Insures Satisfaction 



MARDEN-WILD CORP. 

FRANK W. MARDEN, Pres. 
Somerville Station 

BOSTON, MASS. 




NATURE AND CONTROL OF TANNERY PROCESSES 



Nature and Control of Tannery Processes 

A Practical Exposition of the Purposes and Functions of the Beamhouse, Chrome-Tanning 

and Fat-Liquoring Processes, as Revealed by the Latest Researches, and of the 

Means for the Economic Control of These Processes Within the Tannery 

By Joseph R. Lorenz 



Soaking of Hides 



The purpose of the first tannery process, namely, the 
soaking in water of the green salted or dry hides, is two- 
fold; it may be stated as follows: 

(1) By causing the hides to absorb water, to permit 
the semi-dry condition of the raw stock to return 
to the original moist (and therefore workable) 
condition of the hide in which it was removed 
from the animal. 

(2) To remove by mechanical action the blood, dirt, 
and dung adhering to the hides, and to dissolve 
the salt and any other soluble curing — or pre- 
servative-substances used in the preparation of 
the hides at the slaughter-houses. 

The softening action of the soak is hastened in the 
case of dry hides by the addition to the soak-water of 
caustic soda or sodium sulfide (in the amount of one-tenth 
per cent of either material on weight of stock in the soak) ; 
these materials, by giving rise to alkaline swelling acceler- 
ate the absorption of the liquor by the hides. 

Adhering blood, dung and salt removed from the hides 
remain in the soak-pit; the blood and dung are partly dis- 
solved, while the salt is completely dissolved by the soak- 
water. Those portions of blood and dung dissolved by the 
water (collectively termed "dissolved organic matter") fur- 
nish a medium (i. e., a vehicle) for the propagation of the 
micro-organisms (namely, bacteria, bacilli, etc.,) that are 
carried into the soak-liquor by the hides. The majority 
of the micro-organisms originally in contact with the hides 
belong to species which — while possibly including some of 
pathogenic (i. e., disease-producing) origin, — are harmless 
in character insofar as their action on the hides is con- 
cerned. Accompanying the various harmless types, how- 
ever, are other micro-organisms known as "liquefying 
bacteria" which, through the action of enzyme-substances' 
which they secrete, indirectly have the power of dissolv- 
ing protein-bodies (such as albumin, hide-substance, etc.), 
especially in weakly alkaline media. In a freshly-used 
soak-liquor the number of liquefying bacteria present is 
generally small; the nutrient-substances in the form of 
the blood and the dung introduced by the hides, however, 
cause a rapid multiplication of the original few; at the 
same time, the enzymes secreted by these bacteria are 
actively at work digesting the said nutrient-substances, 
and further, in splitting up the complex chemical struc- 
ture of these into products of a simpler chemical construc- 
tion. In the course of a few days, where repeated use is 
made of the same soak-liquor, the family of liquefying bac- 
teria will have grown to such dimensions that the supply of 

' Enzyme: The active principle of digestive fluids secreted by 
living body cells; examples of enzyme-substances are pepsin and 
rennin (found in gastric juice), and ptyalin (amylase) — the diges- 
tive principle of saliva. 



blood and dung furnished them becomes inadequate; at 
this point, therefore, the enzyme-bodies produced will at- 
tack the hides in the pit, and, in the process of supplying 
their mother-bacteria with additional nutrient-material, 
they will cause a loss of hide-substance, and, ultimately, 
the total destruction of the hides. It follows from this that 
the more or less common practise of using the same soak- 
liquor for successively treating a number of packs of goods 
is, by nature, a wasteful process; for, as the "mellow" 
property of an old soak-liquor is seen to depend on the 
activity of the bacterial enzyme-bodies which it contains 
so will the extra softening-effect be gained only at the ex- 
pense of much hide-substance lost in the process. 

Except common salt, many of the curing — and pre- 
servative substances dissolved from the hides during soak- 
ing are known to have a solvent action on hide-substance, 
especially in medium dilutions'; if allowed to accumulate 
(as in the case of an old or "mellow" soak-liquor), their 
presence, including that of common salt, will interfere with 
the proper swelling of, and absorption of liquor by the 
hides. (See the role of salts in the Pickling and Chrome- 
Tanning Processes.) 

Analytical Control. The analytical control of the soak- 
ing process is ordinarily confined to those eases which, for 
any reason, require the use of the same soak-liquor over 
and over again. The determination of the quantity of dis- 
solved organic-matter accumulating in such liquors should 
be made from time to time, as indicating the extent to 
which the liquefying organisms present are being encour- 
aged to thrive. (It might b© suggested here that by the 
judicious use of germicidal materials which are also capable 
of acting as anti-ferments, all the micro-organisms present 
In the liquor might be rendered innocuous, and further de- 
structive action by the enzyme-bodies stopped. The possi- 
ble hardening or "tanning" effect upon hide-substance of 
any germicidal substance emplo.red should, of course, be 
taken into consideration.) The nature of the salts, and 
the quantities of these and of common salt dissolved by 
the soak-liquor may also be determined, if desired. \\Tien- 
ever the concentration of the salts is found to interfere 
with the proper swelling of the goods, it may be reduced 
by the addition of fresh water to the liquor in the pit. 

= II. i:. rrooti.T— "Leather Industries Lahoratnrv 11. ...l;." 



J. BRISK « COMPANY 

SODIUM SULPHIDE ALUMININA SULPHATE 
SODIUM BICROMATE POTASH CH ROM E ALU M 
GLAUBER SALTS EPSOM SALTS 

Tanners' Chemicals of all kinds. 

155 N. Clark St.. CHICAGO 



10 



NATURE AND CONTROL OF TANNERY PROCESSES 



It takes them 
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ARMAND SCHMOLL 

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4 1 Park Row, corner Spruce St. 

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Cable Address: PROMPTER, New York 



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fXCORPORATED 

1 54 Nassau Street, New York 



NATURE AND CONTROL OF TANNERY PROCESSES 



11 



First Fleshing 



Hides having much surplus flesh and tallow attached 
require a thorough fleshing before being placed into the 
lime liquors. The importance of ridding the hides at this 
stage of every trace of tallow, especially, is evident from 
two considerations; namely, (1) that the action of lime 
upon the fats is to produce insoluble soaps, and that lime 
cannot, therefore, be depended upon to remove the fats; 
and (2), that the form of blemish known as "fat-spue" ap- 
pearing on the surface of the finished leather has been ob- 
served by W. Fahrion' to arise most frequently in the pres- 
ence of the "crystalline" fats (stearin and palraitin), of 
which tallow is composed, rather than from the constitu- 
ents of the fish oils normally used in the fat-liquoring of 
the leather. 

Chemical Behavior of Acids, Alkalies, and Salts 
Employed in Tanning 

For the purpose of enabling the non-technical reader 
to form a true mental picture of the coui'se of action of the 
liming, deliming, pickling and chrome-tanning processes, 
an explanation will be attempted, first of all, of those 
fundamental chemical principles upon which the mechan- 
ism of these processes rests. 

The reader (assuming he is not already familiar with 
the subject) is therefore asked to consider, briefly, the 
chemical structure or "make-up" of the simpler acids, alka- 
lies (or "bases"), and salts. It would be found, first, that 
every acid, alkali, and salt is chemically constructed of 
two principal components, consisting of groups of certain 
chemical elements examples of which are hydrogen, oxy- 
gen, sulfur, chlorine, calcium, sodium and potassium, these 
groups being known as "radicals;" secondly, that these 
groups exist within every acid, alkali, and salt, irrespective 
of the number or variety of indivldua! elements which the 
substance may contain. 

Now, when any acid, alkali, or salt is decomposed (i. e., 
caused to he "broken-up" into its constituent parts), it will 
be evident that the immediate products of the decomposi- 
tion wiU consist, — not of the individual elements of which 
the substance was composed. — but, instead, of the two 
groups or radicals, in which these elements may still be 
found residing. In other words, the first step of the 
"breaking-up" process, in general, will do no more than 
separate the groups in the compound, the groups them- 
selves remaining intact. For the purpose of this discus- 
sion, the foregoing principle, upon which the course of 
chemical reactions, in general, may be said to depend, may 
be stated as follows: The behavior of the chemical groups 
or radicals composing any chemical compound Is, In gen- 
eral, that of primary, or elementary bodies. 

Taking for consideration the principal acids, alkalies 
and salts employed in the tanner>-, it is possible to estab- 
lish a connection between the physical properties (e. g., 
taste) of these and their chemical structure. Thus, acids 
are familiarly associated with a sour taste, alkalies with 
a "caustic" or "soapy" taste, and salts with a saline or 
bitter taste; again, the chemical formula of sulfuric acid, 
for example, is H.SO, (meaning the combination of two 
parts of hydrogen with one of sulfur and four of oxygen), 
while that of hydrochloric (or "muriatic") acid is HCl 



(or, one part of hydrogen combined with one part of 
chlorine). In each of the formulae of the two acids named 
it will he noted that the element hydrogen is written first; 
if the whole list of acids were surveyed It would be found 
that hydrogen is a common constituent of all. Hydrogen 
is, therefore, a "group-element" with respect to the acids. 
To the "hydrogen-radical"*, as this group is called, then, is 
due the "acidity" or sour states of the acids. In the case 
of the family of alkalies, of which ordinary slaked lime 
(or calcium hydroxide), caustic soda (or sodium hydrox- 
ide), and aqua ammonia (or ammonium hydroxide) are 
some of the best known members, that particular chemical 
radical which determines the "causticity" (or "alkalinity") 
of these substances may, on inspection of their chemical 
formulae, be readily identified; the formula of lime is 
Ca(OH), (meaning the combination of two parts of the 
oxygen-hydrogen group with one part of the metal cal- 
cium) ; that of caustic soda is NaOH (wherein one part 
of the oxygen-hydrogen group is united to one part of the 
metal sodium, whose symbol is Na) ; while that of aqua 
ammonia is NH^OH (wherein the oxygen-hydrogen group is 
attached to the ammonium-radical, the latter being con- 
structed, as the formula shows, of one part of nitrogen, 
and four parts of hydrogen). Clearly, then, the common 
radical of the alkalies, and the one to which these bodies 
owe their caustic property and "soapy" taste, is the oxygen- 
hydrogen group, or better known as the "hydroxyl-radical." 
To consider, finally, the remaining class of substances, 
namely the "salts." A salt is produced whenever an acid 
combines with an alkali, or vice versa, the process being 
the familiar one of "neutralization." The following equa- 
tion, which is typical of all neutralization reactions, shows 
how a salt is produced. 

H,SO,-f2(NaOH)=Na3SO,+2(H,0) 
Acid-fAlkali=Salt-(- Water 

In this equation it will be noted that the SO,-radical of the 
acid has united itself to the Na^-radical of the alkali, these 
together forming the "neutral" salt Na,So, (sodium sul- 
fate, or "Glauber's Salt") ; simultaneously, the hydrogen- 
radical (Hj) of the acid has attached itself to the hydroxyl- 
radical (20H) of the alkali, the two thus combining to form 
water. (The fact that might be pointed out as of interest 
here is that the two last-named groups, to which the power 
of all acids and alkalies respectively, is due, are merely 
the constituent parts of that well-known substance — 
water.) Compared with either the acids or the alkalies, 
the salts are much the more stable (i. e., chemically inac- 
tive) substances, a firmer union existing between the 
groups that compose a salt; again, the saline or hitter 
taste of a salt is not due to any one of its two significant 
groups, but resides in the combination of these as a 
whole. 

It now remains to be explained why some acids are 
chemically more powerful or "stronger" than others, or why 
the alkali lime, for instance, is so much weaker in action 
than the alkali caustic soda. As any one who has ever 
experimented with chemicals knows, a perfectly dry sub- 
stance is entirely without action upon another perfectly 
dry substance; on dissolving the first substance in water, 
however, and adding to it the second substance also dis- 
solved in water, chemical combination between the two 



group of the alkalies. 



NATURE AND CONTROL OF TANNERY PROCESSES 




TANNERS SAY: 



Our Liquid Quebracho Extracts — 

Q. P. 
PICKLE SHEEPSKIN SPECIAL 

and 

SNOW WHITE 

Will produce more leather and of a better 
quality than any other Quebracho Extract on 
the market. 

Try it! 

QUEBRACHO PRODUCTS CO., Inc. 

Manufacturers of 

Clarified and Decolorized Liquid Quebracho 

Extracts 

39-4 • CORTLANDT STREET 
NEW YORK CITY 

Factory, Staten Island. N. Y. 



MATURt AND CONTROL OF TANNERY PROCESSES 13 

substances may be at once effected. That water must be tion, and this limit is, therefore, a measure of the chemical 
present in order to cause two chemicals to combine is, power or "strength" of that substance. Thus, for Instance, 
therefore, evident". Now, the part that water plays when the number of hydrogen-radicals (or acid-groups) that be- 
any acid, alkali or salt is dissolved in it is simply this: come released when the different acids are dissolved in 
Water causes the two chemical groups or radicals com- water (and. hence, the relative "strengths" of these acids) 
posing the compound to disunite and become separated". has been determined for each of the acids named in the 
Only when thus separated, or "released for duty," as It appended table, as follows: 
were, are the radicals of one chemical compound able to ^^.j^ Relative Strength 

combine with the radicals similarly released from another Hydrochloric 200 (approx.) 

chemical compound. Plainly, then, once a chemical com- Sulfuric 200 (approx.) 

pound is dissolved in water, it must exist in that first stage Oxalic 0.1 

of decomposition to w-hicli reference was made at the be- Formic 0.0214 

ginning. For illustration, taking the composition of sul- Lactic 0.0138 

furic acid as H,SOj, that of a solution of this acid in water Acetic 0.0018 

would read : Butyric ' 0.00115 

(Hj) + (30.) + (Water) + (Unchanged HjSOj) °a. Boracic 0.0000001 

Thus, while a portion of the total quantity of acid dls- •, ,• ^ ^ ., , • ^u i . *i, ■ 

^ .... ^ „^ The acids listed are thus arranged in the order of their 

solved becomes dissociated, yielding its H, — and SO. — .. ^ „ „ ,* -,i u * j ^i, * *i, * • , „ 

. , " . . ,. "strengths. It will be noted that the two mineral acids, 

groups to the water, the remainder escapes dissociation: , , j ,, ■ , ,^ ■ ,_ . . , 

namely, hydrochloric and sulfuric, are each approximately 

that is, its H, — and SO. groups remain united in the pres- ^ ^, , ^. „ ^ ,, ^, ., „ . 

* " ^ ^ ^ two thousand times "stronger" than the "strongest" or- 

ence of the water. Disregarding this latter portion, there . ., , ,.,.., . ., 

. . game acid, namely, oxalic; formic acid comes next, then 

are found in the dissociated portion the "active gi-oups; , ^. .. , , ^ . ., u-, i_ ■ -j i 

, . , . , lactic, acetic, and butyric acids, while boracic acid, al- 

that is, those groups capable of entering into chemical ,, . -j „ • 4. ,, .i, .. , 1,. -j 

,, , , . though a mineral acid, is seen to be the weakest acid 

union with other substances. Now, the number of groups . „ j ..u ,■ j i, 

of aU; compared with oxalic acid, boracic acid possesses 

that water is capable of releasing vanes with every chemi- . „ . 

but one-millionth the strength of oxalic acid! 

cal substance; in other words, irrespective of how concen- ,1-1 ^, ^-^ ■ x, ,. x xt „ 

, ' „ , , X. , ,x In like manner can the difference m the "strengths" 

trated or strong the solution of an acid, alkali or salt „ ,, . ,, ,- v , . j . x, ,. 

of the various alkalies be explained. In the absence of 

might be made, for every such substance there is a fixed x , „ 7 -x 1, x x j x, x * x, 

actual figures', it may be stated that, of the common alka- 

limit to the niiiiili. !■ i.f "active" groups present in the solu- ,. ,. x , , x ■ u j . , > . x,. ., x 

lies, caustic potash (potassium hydroxide) is the strong- 

ch™ica!"re/,.',V:, ^ V .'''a 'o^dim-TrAempera^m^^^^^^^ ""'"'' °^ ^st"; caustic soda is next in order, then slaked lime, and, 

» This sfii, 11,11 : I .l^ase" by water of the chemical groups finally, aqua ammonia. 

iu a dissolvefl sulistaiioe, is technically known aa "dissociation." 

"a Sulfuric acid actually dissociates into H-I-H.S04. For prac- : See. however, "Tabulation of Hydrogen and Hvdroxvl-ion 

tieal purposes, however, the dissociation products of this acid may concentration of Some Acids and Bases."— xiithur W Thomas 

he regarded as consisting of H,— and SO.— groups. Jour. A. L. C. A.. 15, 133 (1920). 



New York Hide and Skin Merchants 


NEW YORK - BOSTON - CHICAGO 

I. DOERFLINGER 
BROKER 

Foreign arid Domestic Hides and Skins 

Tanning Materials 

Tribune Building New York City 


FEARON, BROWN COMPANY 

CHINA 

GOATSKINS AND HIDES 

96 Wall Street New York 

Phone, John 4(l:;(( 


FREDERICK TAUBER 

FOREIGN 

HIDES AND SKINS 

100 Gold Street New York 

Phone, Beel<man 0494 


Established IXTi; 

STERNFELD, WEIL « CO. 

Hides, Skins, Tallow and Wattle Bark 

Philadelphia Address, 345 North 3rd St. 

154 Nassau St., New York 


Cable Address, "Stonehide." Tel.. Beclunan aSC'.i. 

W. W. JOHNSTONE 

Foreign and Domestic 

HIDES AND SKINS 

154 Nassau Street New York 


DOHERR. GRIMM « CO., Inc. 

87 Gold Street. New York 

Specialists in 

GOATSKINS AND SHEEPSKINS 

From China. Kast India, Africa. Australia and New Zealand 


ANTHONY R. KOSSMANN 

Commission Agent 

HIDES AND SKINS 

Hide and Leather Building 

1 00 Gold Street New York 


Deccan Trading Company, Ltd. 

Importers of 
EAST INDIA GOAT AND SHEEPSKINS 

American Offices 
BOSTON NEW YORK PHILADELPHIA 

00 South St. .<?n Gold St. 402 Arch St. 



14 NATURE AND CONTROL OF TANNERY PROCESSES 

|llllllllllllllllllllllllllllllllllllll!lllllllli 

I IT NEVER VARIES— I 

I IN PULVERIZATION— IN PURITY— IN STRENGTH | 

R-R I 

Chemical Hydrated i 

LIME I 

for use in the unhairing Hquor. ^ 

= R-R CHEMICAL HYDRATED LIME never varies in its purity or strength. It is finely pulverized, blending ^ 

= quickly and smoothly into the liquor. It has reached that state of standardization where all chemical un- = 

^M certainty is eliminated. ^ 

= Ready for easy handling in 50 lbs. self-sealing bags; these containers keep the chemical strength intact ^ 

= and the moisture out. There is no possibility of the contents sifting from the bags to the floor. = 

= R-R CHEMICAL HYDRATED LIME comes also in stout barrels. Adequate testing samples sent to tanners J 

= requesting them. ^ 

I ROCKLAND & ROCKPORT LIME CORP. | 

g ROCKLAND MAINE = 

^ M.;W YORK. 101 !• AKK AVF.NrE BOSTON, 45 MILK STREET ^ 

llllllllillllllllillllllllllllllllllllllllllli^ 




Says an eminent tanning authority: 

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Leading tanners prove the truth of this WHITE STAR 

statement by using ^^^^^bmhm^- CHEMICAL 

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LOUISVILLE CEMENT COMPANY, Incorporated 

Speed Building Louisville, Kentucky 



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FOR 

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Main Office & Warehouse New York Office 

9 Cayudetta Street Hide & Leather Building 

GloversvUle, N. Y. 100 Gold Street 



NATURE AND CONTROL OF TANNERY PROCESSES 

The Liming Process 



The primary purpose of the liming process is, of 
course, familiarly known; it is to effect the removal of 
the hair on the hides. That the liming process, in addi- 
tion to loosening or destroying the hair, causes at the 
same time a change in the character of the hides, is a fact 
also known to all tanners. The various phenomena ob- 
served in the treatment of hides with a "straight" lime- 
liquor (i. e., a saturated solution in water of slaked lime 
only), for instance, are the following: 

(1) Swelling, or increase in weight and volume of the 

hides caused by the absorption of the lime-liquor. 

(2) Plumping effect, or change from the soft and 
yielding state to a more elastic or "rubbery" 

state. 

(3) Loosening of the hair at the roots. 

Aside from these visible phenomena there occur In 
liming a number of reactions which can be tested chemi- 
cally; of these, some may be said to be well defined, while 
their connection with the phenomena of swelling, plumping 
and unhairing has been, of late, established by a number 
of investigators. 

To begin with the lime-liquor itself, it is known that 
the solubility of lime in plain water is very slight; at 32° 
Fahrenheit, for instance, 100 parts of water dissolve but 
17/100 of one part of slaked lime; moreover, and contrary 
to the general tendency, the solubility diminishes with in- 
crease in temperature; thus at 212° Fahrenheit it becomes 
8/lUO per cent, or less than one-half the solubility it pos- 
sesses in water at freezing temperature'. By reason of 
its slight solubility, therefore, of the relatively large quan- 
tities of lime employed in practise, by far the greater 
portion remains undissolved (or suspended) in the lime- 
liquor; as the dissolved portion is removed from solution 
by the hides, however, more of the solid lime passes into 
solution, the latter being thus kept in a saturated condi- 
tion (i. e., at maximum concentration) at all times through- 
out the process'. 

When lime is dissolved in water, the two chemical 
groups composing it, viz.. Ca and (0H)2, become separated 
(or dissociated) in the manner already described; thus ex- 
isting "freed" within the lime-liquor these groups are pre- 
pared for action — each in the direction peculiar to itself. 

The first action, namely, swelling, which ensues when 
the softened hides are placed into the lime-liquor, is pro- 
duced by the hydroxyl, or OH-groups released from the 
lime". In other words, swelling is purely a function of the 
"alkalinity" of the liquor. The swelling power of lime (and 
of alkalies in general) diminishes with rise in temperature 
of the liquors; the explanation of this lies in the fact that, as 
the temperature increases, the hide also becomes less elas- 
tic or "cohesive." In reference to the phenomena of plump- 
ing and unhairing it may be stated that these do not arise 
in any simple manner comparable to that in which the 
swelling of the hide is effected. Broadly considered, plump- 
ing and unhairing find their origin in the joint action upon 
the hide of the two lime groups, plus — in the case of un- 

» V.in Nostrand's Chemio:il Annual — Olsen. 

» This -n-ill. however, not be the case unless some means are 
employ,..! or ai-'itatinj? the lime-liquor during use. 

" \ii ' i ill' -, tlierefore, are capable of swelling hide. Since, 
•;o"'> ■'■ "limiting point" the degree of swelling pro- 

dui-.(i I i.roportion to the number of hydroxvl-groupg 

relc:iM : lil ii: ,i:„s have not the same power to swell hide: thus, 
caustir i,,,i,.ii, Miiirh im solution yields the greatest number of 
these groups, possesses the maximum swelling power of the alka- 
lies, while ammonia— giving rise to the least— is weakest in swell- 
ing action. 



hairing — that of the bacterial enzyme-products formed in 
the lime-liquor soon after the hides are introduced. Again, 
taking the case of the alkalies in general, plumping may 
be said to be more distinctly influenced by the nature of 
the metal-group of the alkali; thus — while the plumping 
and swelling produced by "pure" solutions of the alkalies 
are known to occur simultaneously, both in diminishing 
ratio, from the "strongest" alkali down — plumping is not 
a necessary accompaniment of swelling nor is swelling 
always accompanied by plumping. The unhairing power 
of the alkalies, on the other hand, increases as the alkali 
becomes "weaker"; in other words, caustic potash and 
caustic soda — although exhibiting the strongest swelling 
action — cause least unhairing, while ammonia — possessing 
minimum swelling power — is most rapid in unhairing ac- 
tion. It must not be supposed, however, that this increase 
in depilatory power is gained as a result of the lesser 
hydroxyl-group concentration of the "weaker" alkali: on 
the contrary, the hydroxyl groups, as will be seen, play a 
very important role in the unhairing process; moreover, 
the unhairing power of any alkali will increase in propor- 
tion to the concentration of its solution (e. g., the unhair- 
ing effect of caustic soda may be made to equal that of 
ammonia simply by employing a relatively "stronger" so- 
lution of the soda). The explanation of this paradoxical 
behavior of the alkalies with respect to unhairing rests — 
as it does in the case of plumping — upon the difference in 
the nature of the metal-group by which one alkali is dis- 
tinguished from another. 

In the case of liming, the mechanism of unhairing may 
be described as follows": The hydroxyl-groups in the lime- 
liquor first soften the epidermis (or "outer skin") of the 
hide, and then dissolve it, together with the coriin (or ce- 
menting substance of the hair roots) ; the dissolved epi- 
dermis and coriin, in turn, furnish, a nutrient-medium for 
the bacteria present, enabling these bodies to secrete en- 
zyme-substances, by whose solvent action the hair is still 
further loosened. The process is thus seen to consist of a 
cycle of operations, and it wUl be apparent that the longer 
it continues, the richer must the lime-liquor become in 
enzyme-content, and, hence, the more powerful in unliair- 
ing effect'^. 

Now, as the lime-liquor grows "mellow," the solvent 
action which it normally exerts upon the hide itself be- 
comes greater and greater. A "mellow" lime-liquor thus 
compares with a "mellow" soaking-liquor both causing 
losses of hide-substance. By reason of its alkali-content, 
however, the lime-liquor will be the more destructive of 
the two; in other words, a certain loss of hide-substance 
occurring in the liming process may result from tlie purely 
chemical action of the alkaline liquor. Tbus, in general, 
the greater the concentration of hydroxyl-groups (i. e., the 
more "alkaline" the liquor), the greater will be the loss 
of hide-substance. The one exception to this rule, how- 
ever, is ammonia; far from exhibiting the minimum sol- 
vent action, ammonia causes instead the greatest loss of 
hide-substance". 

Besides giving rise to tbe foregoing phenomena, a fur- 
ther function of the liming process is to remove the seba- 



" The unhairing enzymes are secreted freely in media other- 
wise unfavorable to the rapid growth of the bacteria, such as, 
for instance, lime-liquors. 



-Edmund Stiasny- 



16 



NATURE AND CONTROL OF TANNERY PROCESSES 



Cable A(l<lre> 



nud," »n- York 




FREDERICK FARAONE & CO. 

Direct Importers of HIDES. SKINS — Gl. Produep from 

CHINA, JAVA. INDIA, NO. AFBICA, SPAIN. 

ITALY. BAXKANS, ETC. 

74-76 Gold St., New York 

(I'.vruiiiid lUdg.) 



W. L. MONTGOMERY « CO. 

HIDES AND SKINS 

lo High Street, BOSTON 

Cable Address: "Winsmout," Boston 



EDWARD H.BILL 8 CO. 

Specialize in 
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}:y. 79 South Sf. Boston, Mass. /,' 





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NATURE AND CONTROL OF TANNERY PROCESSES 



17 



ceous (or fat) glands situated at the roots of the hair on 
the hide; the removal of these glands is effected by the 
mild saponifying action which lime exerts upon the fats. 
The removal of these glands should be complete, else 
"spueing" of the finished leather may result. 

Thus far, the action of a "straight" lime-liquor has 
been considered. In modern practise, however, the period 
In which the hides remain in contact with the lime-liquor 
is shortened as much as possible by the employment of 
liquors containing in addition to lime, certain materials 
designed to accelerate the unhairing process. Such so- 
called "sharpening" materials may be divided into two 
groups": 

(1) Those serving to increase the "alkalinity" of the 

lime-liquor. 

(2) Those which form hydrosulflde (SH)-groups. 

The first group of sharpening materials may be fur- 
ther divided into two classes, viz.: 

(a) Substances which in solution yield a greater num- 
ber of hydroxyl-groups than lime alone can pro- 
duce; e. g., caustic potash, caustic soda, ammonia, 
etc. Of ammonia a word may be said here; am- 
monia enters into a loose combination with lime, 
forming a calcium-ammonium compound similar 
to the corresponding barium and zinc compounds; 
in so doing, the "alkalinity" of the liquor becomes 
actually lowered, in consequence of which the 
swelling and unhairing power of the liquor will 
be inhibited. In the presence of lime, therefore, 
ammonia is quite without value as a "sharpening" 
agent, and the belief long held that the ammonia- 
content is a measure of the unhairing power of a 
lime-liquor is, therefore, unfounded. 

(b) "Neutral" salts of bases "stronger" than lime. 
The manner in which these render the lime-liquor 
more "alkaline" may be illustrated by taking the 
case of sodium sulfate (or Glauber's Salt), 
Na^So,; in contact with lime, sodium sulfate re- 
acts with it, becoming itself converted to caustic 
soda, and changing the lime to calcium sulfate, or, 

Ca(OH),+Na,SO,=.2NaOH-|-CaS04; 

thus, in place of the lime will remain the 
"stronger" alkali, caustic soda. 

0£ the second group of sharpening materials, sodium 
sulfide (Na^S) is the most prominent member. Notwith- 
standing the loss of the hair which it ordinarily causes 
(for sodium sulfide attacks keratin — the substance of which 
hair is composed), this material finds favor in the tannery 
on account of the rapidity of its action in loosening the 
hair when employed either alone or in combination with 
lime. 

Dissolved in water, sodium sulfide releases its two 
chemical groups, Na^ and S. which, however, immediately 
combine with the two water-groups, H and OH, to form 
the substances NaOH (caustic soda) and NaSH (sodium 
hydrosulfide), in accordance with the following equation: 

Na,S-fH,0=NaOH+NaSH. 

The caustic soda and sodium hydrosulfide, m turn, be- 
come dissociated into metal groups (Na.), hydroxyl-groups 
(OH), and hydrosulfide-groups (SH). In the presence of 

■' Ecliiu.nd Stiasny— Loc. Cit. 



lime a second metal-group, namely Ca, is further intro- 
duced as a dissociation-product of the calcium hydrosulflde 
(Ca(SH)j) that is formed when lime reacts with sodium 
sulfide". 

The most prominent characteristics of the various 
chemical groups present in a sulfide, or sulfide-lime liquor, 
as enumerated above, have been brought to light by Sti- 
asny", and may be summarized as follows: 

(1) The hydrosulfide-group alone possesses neither 
swelling, plumping nor unhairing properties. 

(2) Only by the combined action of the hydrosulfide- 
and hydroxyl-groups is the powerful unhairing 
effect exhibited by a sulflde-liquor produced. 

(3) The extent to which the swelling, plumping and 
unhairing effects manifested by a sulfide-liquor 
occur depends on the proportion of hydrosulfide- 
groups to hydroxyl-groups present, the most 
favorable ratio being 1 : 1". 

(4) An excess of hydroxyl-groups (i. e., an increase 
in alkalinity) has little effect on the action of 
the liquor. A preponderance of hydrosulfide- 
groups, on the other hand, adversely affects the 
action of the liquor. 

In presence of an excess of hydrosulfide-groups, swell- 
ing, plumping and unhairing are all markedly inhibited. 
In practise, a sulfide-liquor may suffer loss of alkalinity 
through the use of "hard" water in preparing the liquor. 
"Hard" water uses up the hydroxyl-groups, leaving the 
hydrosulfide-groups in excess. The deficiency in alkalinity 
thus produced can, however, be restored by the use of a 
small quantity of lime in admixture with the sulfide. 

It will be noted that the active alkali of both sulfide- 
liquors and sulfide-lime liquors is caustic soda. By reason 
of the ready solubility and powerful action of this alkali 
compared with lime, greater care is necessarily required 
in the use of sulfide-liquors, in general, than would be de- 
manded of a "straight" lime-liquor. Thus, in the repeated 
use of the same sulfide-liquor, the excess caustic soda 
which accumulates in the liquor must be removed. For 
this purpose, prohably the best means Is calcium chloride 

(CaCL)". Added to a sulflde-liquor, calcium chloride de- 
stroys the caustic soda by converting it into common saltr 

(NaCl), at the same time regenerating caustic lime in ac- 
cordance with the following equation: 

CaCL+2NaOH=2NaCl-|-Ca (OH),. 

The action upon hide of a sulfide-liquor has been ob- 
served to differ from that of a lime-liquor In one important 
respect, to wit, that sodium sulfide attacks the keratin of 
the hair, upon which, on the other hand, lime exerts little 
or no solvent action. From this it may be inferred that the 
sweat ducts of the hide, being keratinous in structure, 
would also be dissolved by treatment with sulfide-liquor; 
a "straight" liming treatment, on the other hand, would 
leave the sweat ducts intact in the hide. 

Analytical Control. The following considerations 

>■■ The reaction is as follows: 

ra(OH),-f2.\aOII-f2NaSn=Ca(SH)2-|-4XaOH. 
The fouvcrsion of the lime into the strong alkali, caustic soda, 
explains the increased swelling and plumping action exhitiited 
by a lime-snlHde mixture. 

»« Loc. Cit. 

"Or. the ratio in which these groups are found to exist in the 
material, sodium sulfide. 

" Payne-Pullman Process. In practise, one part of calcium 
chloride to three parts of crystallized sodium sulfide are employed. 



18 



NATURE AND CONTROL OF TANNERY PROCESSES 




ilors for I^eatl 



A Supplementary Text-Book 
on Leather Dyeing 



Every leather dyer should have his copy of "Colors for Leather." 
This loose-leaf volume describes those Du Pont Dyestuffs w^hich 
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Complete directions for application, with samples showing the 
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E. I. du Pont de Nemours & Co., Inc. 

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WILMINGTON. DELAWARE 

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STANDARD 



^VE5TLJFF3^ ^^N gFORMl^^ 



W^ 



NATURE AND CONTROL OF TANNERY PROCESSES 



19 



should govern the procedure employed for the analytical 
control of any particular form of the liming process": 

(1) That the "alkalinity" of a pure lime-liquor in con- 
tact with solid lime remains at a practically con- 
stant point throughout the liming treatment'; 
thus, the alkali-content of iifty cubic centimeters 
of a saturated lime-solution, measured at 60° 
Fahrenheit, will be found to correspond to 23.6 
cubic centimeters of a tenth-normal acid solu- 
tion. A higher figure will indicate the presence 
of one or more of the "stronger" bases, viz., caus- 
tic potash or soda; a lower figure, on the other 
hand, may mean 

(a) that the liquor holds in solution "neutral" 
salts, or decomposition-products of hide-sub 
stance and lime, or both, or 



(b) that the liquor contains 
tion with lime, or 



in combma- 



(c) that the liquor has been insufficiently agitated. 

(2) That the influence of ammonia, formed by the 
action of lime and bacteria upon the dissolved 
organic-matter, is positively detrimental. Where 
the conservation of hide-substance is of any im- 
portance, a lime-liquor that has become strongly 
ammoniacal through repeated use had best be 
drained into the sewer. 

(3) That dissolved organic-matter accumulating in 
the liquors consists of both epidermal matter 
(which it is the function of lime to remove from 
the hides), and portions of the hide itself. In 
the absence of analytical means permitting the 
differentiation of the products of the normal action 
of the lime, on the one hand, from the dissolved 
hide-fibres, on the other. It will be evident that 
the estimation of dissolved organic-matter in 
lime-liquors is of limited usefulness only. For 
control purposes, however, the quantity of or- 
ganic matter normally dissolved by the liquors 
under any given set of conditions during the lim- 
ing treatment may be determined, and losses of 
hide-substance made possible of detection, by any 
Increase which the value thus established may 
show In subsequent runs. 

(4) That the unhairing power of a lime-liquor in- 
creases with the age of the liquor, the age of the 
liquor, in turn, being measured by the amount of 
ammonia and dissolved organic-matter which it 
contains. 

(5) That the unhairing power of a sulfide-liquor, or 
a sulfide-lime liquor, depends principally on two 
factors, viz.: 

(a) the strength of the liquor in terms of sulfide 
(SH); and 

(b) the proportion of sulfide to alkali (SH : OH) 
present. 

In the analysis of siilfide-liquors, therefore, the im- 
portant determinations to be carried out are (1) Sulfide 
as NRjS" and (2) Alkali in combination with the sulfide-" 

WASHING OF LIMED HIDES 

The first step In the removal of lime fi'om the hides 

" See "Tlie Determination of Alkaline SuUiiles in Lime 
Liquors."— Fiui G. A. Enna.— Jour. S. L. T. C, 5, 131 (1921). 
M sge "The Analysis of Lime Liquors."— Donald Burton— Loc 



consists in washing the limed goods, after unhairing and 
fleshing, for a period of one-half hour or longer, in a re- 
volving wheel supplied with a stream of water. 

The maximum washing effect is gained (1) when the 
water used Is quite free from "temporary hardness." and 
(2) when the temperature of the water is kept at the 
proper (or "optimum") point. 

The effect of "temporary hardness" (consisting of 
calcium and magnesium bioarbonates dissolved in the 
water) is exceedingly detrimental. In tlie presence of 
"temporary hardness," the caustic lime, with which the 
hides are impregnated. Is immediately converted into in- 
soluble calciium carbonate (chalk); once formed in the 
hides, calcium carbonate cannot be removed by further 
washing, but will require an acid treatment for its re- 
moval. 

The question of what is the most effective temperature 
of the wash-water cannot, in the absence of specific data, 
be answered definitely. 'WTiile it is true tliat cold water 
will dissolve more lime than warm water, it must be re- 
membered that cold water will also produce the greater 
swelling of the hide, and by thus allowing the hide to re- 
tain more lime-liquor, the action of oold water is to actual- 
ly decrease the effectiveness of the washing. The choice 
of temperature, hence, would appear to be one of compro- 
mise, and luke-warm water, it would seem, should remove 
in a given space of time the greatest quantity of lime from 
the hides. 

The passage of the limed hides througli the unhairing 
and fleshing machines serves to rid the goods of about 
thirty-five per cent of the lime; another thirty per cent, is 
dissolved out during the one-half hour period of washing, 
the lime-content of the washed hides being thus reduced 
to about thirty-five per cent of the original amount. 



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20 



NATURE AND CONTROL OF TANNERY PROCESSES 



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NATURE AND CONTROL OF TANNERY PROCESSES 



21 



Dclimin^ and Bating 



The final beamhouse operation, by which the last ot 
tho non-essential portions of the hide are removed, and 
the hides are made ready for tanning, Is that of bating. 

Bating has for its object ", ": 

(1) The reduction of the swelling of the limed hides. 

(2) The digestion (a) of the elastin fibres present in 
the outer layers of the hides, and (b) of the cementing 
substance surrounding the fibres of the main body of the 
hide. 

In the present-day production of chrome-tanned upper 
leather, deliming and bating are generally carried out In 
one operation by the use of some proprietary preparation 
of the tj-pe of "Oropon," of which the active ingredients 
are (1) ammonium chloride ("Sal Ammoniac"), and (2) 
the digestive principle (tryptic enzymes) extracted from 
the pancreas of hogs and cattle. 

The reduction, in the first place, of the swelling of 
the hides is of prime importance, for hard leather would 
otherwise result were the hides tanned in a swollen state ". 
The first essential of bating, therefore, is the removal of 
the caustic lime producing the swelling, and this is brought 
about by the chemical action of the ammonium chloride 
present in the bating material. Ammonium chloride finds 
preference over a host of other deliming materials be- 
cause 



(1) 



(3) 



it foi-ros with caustic lime one of the few lime- 
salts that are readily soluble in water, namely, 
calcium chloride; 

its base, namely ammonia, which is set free by 
the action of the lime, is known to produce less 
swelling of hide than any other alkali, and 
ammonia can, moreover, be readily washed out 
of hide: 
ammonium chloride is comparatively low in cost. 



The fact should be stated, however, that ammonium 
chloride will not attack any calcium carbonate that may 
have been formed in the hide by the action of "hard" 
water, if the latter was employed in the washing of the 
limed goods. Calcium carbonate, however, being a "neu- 
tral" substance, has no swelling power, and may be con- 
veniently left in the goods until these are placed into the 
pickle, when, by the solvent action of the acid liquor, the 
hide win be freed of the carbonate. 

So far, tlie purely chemical action of the bate in re- 
moving the lime from the hides has received mention. 
True "bating," however, commences when the digestive 
principles in the form of the pancreatic enzymes contained 
in the bate-liquor begin to act upon, and to dissolve the 

" "The Mechanism of Bating." — John Arthur Wilson — Jour. 
Ind. Eng. Chem., 12. 1087 (1920). 

" "The Removal of Elastin During Bating."— Robert H. Mar- 
riott—Jour, S. L. T. C, 5, 280 (1921). 

" Cf. Sole Leather, which receives no bating. 



elastin fibres present in the outer layers of the hide. The 
elastin fibres form the chief support of th grain structure 
of the lilde, and their slow removal causes the grain-mem- 
brane to gradually collapse, producing what is known as 
the "hated-effect." The hide thus becomes flaccid — a de- 
sirable condition, from the standpoint of the tanner, as 
productive of "silky-grained" leather. A further function 
of bating, however, has been described by Robert H. Mar^ 
riott '-' to consist in dissolving the cementing substance 
surrounding tlie fibres of the main body of the hide. A 
portion of this cementing substance is removed during 
liming, and the effect of its complete removal by tlie sub- 
sequent action of the bate would be to cause the hide- 
structure to fall together a little, — thus contributing to the 
"bated-effect" as a whole. The last-described action would 
e.xplain the characteristic effect which bating has upon 
the appearance of the grain-side of the hide, the grain 
showing up pix)minently once the liair-holes and sweat- 
ducts thereon have been opened up and cleared ot gummy 
matter. 

In the modem short-time method of bating with arti- 
ficial materials, destructive tendencies — well-known as a 
feature of the earlier drug bates — may be said to scarcely 
enter. Indeed, it is to be questioned whether any true 
"bated-effect" at all is gained during the extremely short 
period in which the hides are left, for instance. In an "Oro- 
pon"-liquor. Wilson ■'■■ has thus shown that in order to de- 
prive a calf-skin of its elastin fibres it must be digested for 
a period of twenty-four hours in a liquor containing trypsin. 
That the action of the modern bate-liquor is practically 
confined to that of the ammonium chloride present in re- 
moving lime from, and in reducing the swelling of the hide, 
seems, therefore, most likely. 

Analytical Control. The actual measurement of the 
"bating-power" of a bate-liquor cannot be performed by 
any simple means. For this reason, the analytical control 
of the bating process is but seldom practised; the delim- 
ing power of a fresh or used bate-liquor, however, may be 
readily ascertained by chemical analysis. In the beam- 
house, the test for the presence of caustic lime remaining 
in the bated hides may be conveniently made by moisten- 
ing a freshly-cut edge of the hide with phenol-phthalein 
solution, which will turn red in the presence of the free 
alkali. 

" Loc. Cit. 
" Loc. Cit. 



WALTER S. LAPHAM 

Foreign and Domestic 



HIDES 



I Park Row 



New York 



ALBERT HEYMANN & CO. 

41 PARK ROW NEW YORK 

FOREIGN HIDES AND SKINS 



22 NATURE AND CONTROL OF TANNERY PROCESSES 



! 

i YOUR GUARANTE E | 

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I i Weighed and Selected by j 

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NATURE AND CONTROL OF TANNERY PROCESSES 



23 



Method of Ascertaining Weight of Dry Leather-Forming 
Substance in Wet Hides ' 



At the conclusion of one or another of tlie various 
beamhouse processes, it is often desirable to know the 
actual weight of dry leather-forming substance In the raw 
material, and consequently, the maximum weight of leather 
whieh the material may be expected to yield. Calculation 
of the dry weight from the weights of the soaked or limed 
hides leads to variable figures by reason of the variability 
of the swelling of the hides in practise, while actual drying 
and weighing of portions of the hide-material itself is im- 
practicable on account of the impossibility of getting really 
average samples. 

The method to be described is an old one, but is given 
here for the benefit of those who may not know of its ex- 
istence. The method consdsts in weighing the wet hide 
while it is totally immersed in water. The hide is sus- 
pended from the arm of a delicate balance (of ten to fif- 
teen pounds capacity) by means of a thin copper wire into 
the water contained in a pit deep enough to allow the hide 
to hang free from contact with the sides or bottom, and 
its weight in this position is then noted. The weight in 
water of the hide multiplied by 3.38 will be found to equal 
the average weight of the hide when perfectly dry. By 
subtracting the dry weight thus obtained from the original 
wet weight, a true measure is obtained of the amount of 
swelling which the hide has undergone. 







PlgttT* A. 7«rttoal 301 



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Laborat 



Book" 



The Pickling Process 



Next in order after bating comes the pickling of the 
hides. Pickling serves a two-fold purpose: viz., 

(1) it removes from the hide any lime remaining in 
the form of calcium carbonate. 

t2) it imparts to the hide just out of the alkaline 
bate-liquor an acid charge, making the hide re- 
ceptive to the subsequent entrance of the acid 
chrome-tanning liquor by thus preventing the 
precipitation of basic chrome on the surface of 
the hide. 

Pickling is, in a stprfi sense, a part of the chrome- 
tanning process, or, at least, a prerequisite of it. Pickling 
consists in paddling or drumming the bated goods for an 
average period of twelve hours in a one-half to one per 
cent, solution of some moderately strong acid, the solu- 
tion containing, besides the acid, a large proportion (e. g., 
ten per cent.) of common salt. Almost any acid will do, but 
sulfuric acid is preferred on account of its low cost. Using 
sulfuric acid, then, in the presence of an excess of com- 
mon salt, the composition of the finished pickle-liquor will 
include the following substances: viz.. 

(a) Common salt, as NaCl; 

(b) Glauber's Salt, as Na^SO.; and 

(c) hydrochloric acid as HCl, 

the sulfuric acid originally used disappearing from the 
liquor after combining with the common salt present to 



form Glauber's Salt, and releasing its equivalent of hydro- 
chloric acid, according to the following equation: 
H.SO,+2NaCl=iNa2SO.-f2HCl. 

The action of tlie pickle-liquor in removing from the 
hides any lime remaining in the form of calcium carbonate 
depends on that of the hydrochloric acid present, hy which 
the insoluble calcium carbonate is converted into soluble 
calcium chloride. 

Apropos of the second and principal function of the 
pickling process, namely, that of imparting to the hide an 
acid charge, it should be stated, first of all, that hide-sub- 
stance is amphoteric by nature; i. e., hide-substance is 
capable of acting either as a weak base, or as a weak acid. 
Hide-substance, therefore, will combine with either acids 
or alkalies to the accompaniment of- swelling. Now, just 
as the swelling produced by alkalies is known to be due 
to the "active" hydroxyl, or OH-groups released by them, 
so is the swelling produced by acids due to the "active" 
hydrogen, or H-groups, common to all acids. The swelling 
of hide produced by alkalies, on the one hand, and by 
acids, on the other, is similar in all respects save one; 
namely, that while alkaline-swelling is accompanied by 
more or less plumping (or, increase in elasticity) of the 
hide, acid-swelling is attended by little or no plumping. 

In the pickling process, however, the object is not to 
swell tlie hide, but merely to impart to it an acid charge. 
Now, it is known that the degree of swelling is proportional 



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NATURE AND CONTROL OF TANNERY PROCESSES 



25 



to the number of "active" hydrogen, or acid-groups present 
in the liquor; i. e., the more "active" groups in solution, 
the greater will be the swelling of the hide. Were hide 
placed, for example, in a pure solution — however "weak" it 
may be — of one of the strongest mineral acids, such as 
sulfuric or hydrochloric, it would swell so enormously as 
to be in great danger of bursting. The problem, then, is 
that of reducing the number of "active" groups released 
in solution by the acid, and so keep the swelling o£ the 
hide down to a minimum. To this end there fortunately 
exists a simple means, and that consists in putting com- 
mon salt into the pickle-liquor along with the acid. The 
salt is itself dissociated in solution — i. e., its chemical 
groups, namely Na and €1, become released (neither of 
these groups, however, having any swelling action upon 
hide) ; in the presence of these salt-groups, however, a 
lesser number of acid, or hydrogen-groups are split from 
the acid in the liquor, the number of "active" acid-groups 
tluis becoming reduced ". An exact analogy of the forego- 
ing phenomenon may be drawn by taking the case of two 
water-soluble substances. Of the one substance, water 
will dissolve a certain definite percentage, of the other, 
also a definite percentage, which may or may not be the 
same as the first. Now, suppose that the second sub- 
stance was to be dissolved in water already containing in 
solution some of the first substance; in this case, of 
course, less or it could be brought into solution than If 
the water were entirely free from the first substance. So 
it is with regard to the effect of the salt present in the 
pickle-liquor, only here it is not the question of the solubili- 
ties of the salt and acid in water, but that of the dissocia- 
tion of these substances which is of importance. 

The function of the salt in pickling, then, is to inhibit 
the swelling action of the acid upon the hide. Notwith- 
standing, however, the large quantity of salt normally em- 
ployed in pickling, considerable swelling does occur in 
practise. Thus, the amount of liquor which the hides or- 
dinarily absorb along with the acid during pickling has 
been found to average sixty-five per cent, of their drained 
pickle-weight. 

The uniform penetration of the pickle-liquor into the 
goods is of great importance. If, owing to the presence of 
grease in the hide, or to some other cause, certain areas 
do not receive so much acid as the remainder of the hide, 
uneven coloring will result in tanning, the color of the 
chrome-substance deposited in the hide varying in shade 
according to the amount of acid with which it is able to 
combine. 

Analytical Control. In practise, a pickle-liquor is sel- 
dom discarded after being used in the treatment of a single 
pack of goods; instead, for the sake of economy, it is re- 
plenished with more acid and salt, after which it receives 
the second pack of goods; this process may be repeated 
until as many as thirty packs of goods have passed in suc- 
cession through the liquor. In the replenishment of a 
" Law of Mass— .\ction. 



pickle-liquor, careful chemical control is a necessary fea- 
ture. The quantity of acid absorbed by the goods during 
pickling will amount to about 93 per cent of the total 
weight of acid in the liquor; this figure, however, is by no 
means constant, and unless the amount of acid left in the 
liquor is accurately known, too little or too much may be 
added when the liquor is replenished. For practical pur- 
poses, however, it is quite suflScient to check the acid- 
content of a pickle-liquor after the passage of every four 
or five packs of goods through it. The quantity of salt 
removed along with the acid by the goods from the pickle- 
liquor is approximately 25 per cent of the amount dis- 
solved in the liquor. The actual quantities of both common 
salt and Glauber's salt removed depend upon the concen- 
tration in which these salts existed in tlje liquor, and are 
proportional to the quantity of liquor simultaneously ab- 
sorbed by the hides. Below are given some typical figures 
obtained in practise (by chemical analysis of the used 
liquors), showing the amounts of common salt and of 
Glauber's salt removed by the different packs of goods 
(all being of practically uniform weight) as these were 
passed in succession through a pickle-liquor — originally 
containing 1,800 pounds of common salt — which was re- 
plenished, as each pack was removed, with acid and addi- 
tional salt in the amounts shown in the last column: 

Pounds Removed from 
Liquor by Each Pack 

^ a Pounds per 

^ w , Pack of 

Order of Packs go 't; m Common Salt 

5 ■Z ■^ ^ with which 

§ S I S Liquor was 

■w ■" Replenished 

1st 425 10 

2nd to 4th 390 47 300 

5th to 9th 365 72 330 

10th to 14th 366 81 390 

15th to 21st 375 88 400 

In restoring the salt-content of a used pickle-liquor to its 
original value, it is usually most convenient to employ the 
hydrometer, the specific gravity reading of a fresh liquor 
at 60° Fahrenheit being normally about 1.07, or 9.5° Baume. 
If, however, the total volume of the liquor is known, it is 
more accurate to determine the salt-concentration by chem- 
ical analysis of the liquor. 

The percentage of acid and total salts present, as 
found by analysis, when taken together, will give some idea 
of the rate of action and swelling power of a pickle-liquor. 
The direct measurement of the swelling power, however, is 
best performed by means of the electro-metric method, and 
this is the most accurate for the purpose, measuring, as it 
does, the actual number present of free hydrogen-groups, to 
which the swelling property of the liquor is due. 



NATURE AND CONTROL OF TANNERY PROCESSES 



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NATURE AND CONTROL OF TANNERY PROCESSES 

The Chrome-Tanning Process 



27 



The function of the chrome-tanning process, like that 
of the vegetable, or any other form of tanning process, is 
that of converting the raw hide into leather; i. e., wiUi- 
out altering the essential form and structure of the hide, 
of changing its easily decomposable substance to another 
of an imputrescible nature. 

The chemistry of chrome-tanning is linked with that 
of alum and iron-tanning, the three elements, namely, 
aluminium, chromium, and iron having similar properties, 
and being therefore placed into one chemical family. Es- 
sential differences, however, exist between the action upon 
hide of the three substances named; alum, for instance, re- 
mains combined with hide only so long as the leather is 
kept out of water; in other words, alum may be readily 
washed out of hide ; iron-tannage Is more stable than alum- 
tannage, yet not so permanent as chrome-tannage. Chrome- 
tannage, it may be safely assumed, is the most enduring 
of all forms of tannage hitherto discovered, including that 
of the older vegetable or bark processes. 

The chemical compounds of chromium are numerous 
and varied in character. All chromium compounds are 
highly-colored; this fact giving rise to the name of the ele- 
ment from the Greek word "chroma," meaning color. 
Among the important salts of chromium are (1) the chro- 
mates — of the type of sodium cihro-mate, Na-^CrO,, which is 
yellow in color; (2) the dichromates — formed by treating 
chromates with acid — of which sodium dichromate, 
Na.,Cr,0„ is an example, and which are usually orange in 
color; and (3) the chromic compounds, e. g., chromic sul- 
fate, Crj( 304)3 — formed by reducing (i. e., depriving of oxy- 
gen) the dichromates in the presence of acid — which are 
green or violet in color. Chrome-salts dissolved in water 
ai-e, as a rule, acid in character. In the case of the dichro- 
mates this may Be explained by the fact that the chromic- 
acid group (CrOj) which is released in solution is a rela- 
tively much "stronger" substance than the accompanying 
basic-group, namely Na, which also is set free; in the case 
of the chromic-compounds, chromium (Cr) forms the base, 
while the acid is generally sulfuric, or hydrochloric; the 
acid groups (in this case SO, or CD which are here re- 
leased in solution, being again in excess of the relatively 
"weaker" chrome-groups, cause the solution again to have 
acidic properties. 

Relative to the tanning effect of chromium compounds, 
it is a well-known fact that only the chromic-salts possess 
the property of converting raw hide into leather; i. e., 
only when in its "reduced" state will chrome combine with 
hide in such a manner as to remain fixed and be resistant 
to the action of water. 

Practical chrome-tanning is divided into two general 
processes, namely, the "two-bath" process, and the "one- 
bath" process. Either of these processes yields a leather 
readily distinguishable from that produced by the other; 
that produced by the "two-bath" process being soft and 
light-colored, that tanned by the "one-bath" process being 
firm and darker in color. The nature of "one-bath" tanning 
is, moreover, slow and progressive, while that of "two- 
bath" tanning is sudden and complex. 

"Two^ath" tanning, as the name implies, is carried 
out in two liquors. The hides are first drummed in a solu- 
tion of sodium dichromate and sulfuric acid until "struck 
through," i. e., until the dichromate-acid mixture has uni- 
formly penetrated the goods. The action of the acid upon 
the dichromate is to form chromic acid (HjCrO,), in ac- 
cordance with the following equation: 

Na2Cr20i-fH=S044-H20=2H,CrO,-fNa,SO,. 



Tlie chromed hides are now drummed in a second 
liquor containing sodium thiosulfate, or "hypo," (NajSjOj), 
and sulfuric acid, which serves to "reduce" the yellow 
chromic acid in the hide to green chromic sulfate, 
Cr(0H)S04, by which the hides are converted into leather. 
The action which takes place may be represented thus": 

2HX'rO, + 3NaA03-f2H,SO,= 

2Cr(OH)SO.-t-3Na,SO,-f3HjO + 3S. 

The free sulfur (S) that is liberated in the foregoing 
reaction — being the product of a side-reaction between the 
sulfuric acid and sodium thiosulfate (viz., H.SOi+Na.iSj02= 
S-fSO.-l-HjO-l-NajSO,) — is deposited within the interior of 
the hide, and, acting as a lubricant, gives to the leather the 
soft feel, and also the light color characteristic of "two 
batli"-tanined leather. Certain precautions are necessary 
in the tanning of hides by the "two-bath" method. In the 
first place, chromic acid is a powerful oxidizing substance, 
having potential destructive tendencies in the presence of 
all organic matter, including hidensubstance. The yellow 
chromed hides should not he exposed to light for any 
longer period than is necessary, for the destructive action 
of the chromic acid is said to commence in tlie presence 
of strong sunlight"'. "T"wo4>ath" tannage finds application 
In the production of inner-sole splits and linings, glove- 
leathers, etc.— in general, whenever a soft leather is 
required. 

In the "one-bath" process of chrome-tanning, the 
chrome is not reduced within the hide, but is present in 
already-reduced form in the liquor in which tlie hide is 
tanned. A "one-bath" chrome-liquor is, therefore, green or 
violet in color. The principle of "one-bath" tanning de- 
pends upon the impregnation of the pickled hides by a 
solution of chromic sulfate (or. rarely, chromic chloride), 
which is acid at first, but later in the process is made 
"basic" (i. e., reduced in acidity) in order to "fix," or render 
insoluble, the chrome compound absorbed by the hides. 

"One-bath" chrome-liquors are prepared, either (1) by 
dissolving in water some proprietai-y preparation in dry 
form of tlie type of "Tanolin," (the latter consisting of 
basic chromic sulfate in admixture with sodium sulfate 
and other substances), or (2) by "reducing" a dichromate- 
Eulfuric-acid solution prepared in the tannery with 

(a) sodium thiosulphate; or with 

(b) sodium bisulfite (NaHSOj) ; or with 

(c) gaseous sulfur dioxide (SOj); or w^th 

(d) cane sugar, or glucose; or with 

(e) glycerine; or with 

(f) a mixture of two or more of the aforenamed sub- 
stances. 

When the reduction of the dichromate-acid solution Is 
effected by means of the first substance, namely sodium 
thiosulfate, free sulfur is formed, and will remain sus- 
pended in the finished liquor; sodium bisulfite and gaseous 
sulfur dioxide, on the other hand, yield chrome-liquors that 
are free from sulfur, such liquors being used whenever an 
especially firm, and "tight" leaUier (e. g., "patent" leather) 
is desired. Cane sugar, glucose, and glycerin, being or- 
ganic materials, behave in a different manner in contact 
with the chromic-acid mixture than do the inorganic ma- 
terials referred to above (as a. b. and c); the chrome, it 



28 



NATURE AND CONTROL OF TANNERY PROCESSES 



f IRC ^ 

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I SUPREMO 

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Exportacion i 



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NATURE AND CONTROL OF TANNERY PROCESSES 



29 



Is true, becomes reduced as before, but much less heat is 
evolved la the reaction'", while less than half the quantity 
of the sugar or glycerin employed is "used-up" (i. e., be- 
comes oxidized) by the chromic acid, the finished chrome- 
liquor being usually violet in color. On account of the 
presence of the excess reducing agent and the aldeliydic- 
oxidation-products formed by the action of the chromic- 
acid upon the sugar or glycerin, and also because the 
chrome in such a liquor is present in modified form, a 
sugar or glycerin chrome-liquor is "milder" (i. e., less 
asitringent) in action (also less uniform in composition) 
than a "hypo" or bisulfite-reduced liquor, and is used prin- 
cipally in the production of the finer leathers, namely, 
calf and kip. 

The color of the reduced chrome-liquor has been 
described as being either green or violet. Violet chrome- 
liquor, for instance, may be formed by dissolving any re- 
duced chrome-salt (e. g., chromic sulfate) in cold water. 
Green chrome-liquor, on the other hand, may be made, 
either by dissolving the chrome-salt in hot water, or by 
heating to boiling the violet solution. Now, in chemical 
composition, botli the green and violet chrome solutions are 
identical. The green chrome-liquor, however, is found to 
produce greater swelling of hide, and to tan more rapidly 
than the violet liquor. The explanation of this dissim- 
ilarity in action between the two chrome substances is 
found in the difference between the dissociation-coeffi- 
cients of (i. e., in the number of chrome and acid-groups 
released in solution by) the two substances; thus, the 
dissociation-coeflicient of the green solution hais been 
found to be more than ten times that of the violet solu- 
tion; i. e., more than ten times the number of chrome 
and acid-groups are released within the green chrome- 
liquor, than are split from the violet salt in solution. This, 
therefore, explains the greater activity or "astringency" of 
"hypo" or bisulfite chrome-liquors which, being formed at 
boiling temperature, are green in color, than that of sugar 
or glycerin liquors which having been produced at lower 
temperatures, are therefore, violet in color. 

The tanning constituent of "one-bath" chromerliquors, 
namely chromic sulfate, has been refeiTed to as being 
present in the liquor in dissociated form; i. e., it exists in 
the form of its two separated chemical groups. The com- 
position of these groups, however, is not constant for every 
kind of chrome-liquor, but varies with the "basicity"" of 
the liquor. Thus, if the "basicity," as determined by chem- 
ical analysis, reads, for instance, 0.63, the liquor contains 
pure chromic sulfate (Cri(S0,)3) only; if the "basicity" 
is 0.95, the dissolved chrome compound has the compo- 
sition Cr2(SO,)2(OH)j — known as the "firstrbasic-chromic- 
sulfate" — this being formed by the addition to the liquor 
of just the right amount of some alliafine substance (such 
as caustic soda), of which the effect is to replace one of 
the SO,, or "acid"-groups in the chromic sulfate with two 
hydroxyl, or OH-groups derived from the alkali; finally, if 
the "basicity" of the chrome compound is found to be 1.89, 
its chemical formula would read Crj(SO,) (OH), — this being 
known as the "second-basic-chromic-sulfate" — and in this 
it will be seen that two of the three 90,-groups originally 
present have been replaced by tour O.H groups from the 
alkali. Chrome-liquors having intermediate basicity-values 
consist of a mixture of two, or, possibly, of oven three of 
the compounds described. Now, as the "basicity" of the 
chrome substance increases, its solubility in water dimin- 



ishes; i. e., ^.he more OH or hydroxyl-groups there are 
added to the chromic sulfate, the less soluble does the lat- 
ter become. On this extremely valuable property of the 
chromic compounds does the principle of "onenbath" tan- 
ning depend. The final chrome-product which would be 
obtained were all three of the SO,-groups in chromic sul- 
fate replaced by OH-groups — in other words, were the 
chromic sulfate completely "neutralized" — is chromic hy- 
droxide, Cr,(OH)„ — a quite insoluble substance, but one 
also devoid of tanning properties. 

Whichever method of preparing a "one-bath" stock- 
liquor is employed, the tanning liquor made therefrom 
should contain an amount of chrome equivalent to approxi- 
mately two per cent of chromic-oxide (CrjOj), or four per 
cent of sodium bichromate on the drained weight of the 
pickled hides. Approximately one-third of this amount of 
chrome is dissolved in the liquor into which the hides are 
entered, the remaining two-thirds being added in two or 
four doses at intervals of every hour or half-hour. (AH of 
the chrome is not added to the liquor at one time, for that 
would produce too rapid surface-tanning, and so hinder 
the penetration of the chrome into the interior of the hide.) 
The "acidity" of the tanning-liquor at the start should be 
so adjusted that the proportion of chromic-oxide to acid 
(CrjOj : SO3) is approximately 1:1; in other words, the 
"basicity" should average 1.00. The concentration (i. e., 
the "strength") of the liquor, in terms of chromic-oxide, 
may vary, — in the case of paddle-tanning, from one-half to 
three-fourths per cent; in that of drum-tanning, from one to 
one and one-half per cent. In addition to the chrome, the 
tanning-liquor should contain about one-third pound of 
common salt, or Glauber's salt, or a mixture of both, to 
one gallon of the liquor. The specific gravity reading of 
chrome paddle-liquors may vary from 5° to 9° Baume. 

From the foregoing it will be noted that the percen- 
tage of "neutral" salts (viz., common salt and Glauber's 
salt) dissolved in the tanning-liquor is only about one-half 
of that required by the pickle-liquor previously described. 
The immediate effect upon the pickled hides of this re- 
duced salt-concentration of the chrome-liquor is to cause 
the hides to swell still further; thus, in practise, where 
the pickled hides have absorbed sixty-five per cent of 
pickle-liquor, they will absorb, in addition, during the 
tanning process ten or twelve per cent of the chrome- 
liquor. It is of no advantage to have more salt present 
in the chrome-liquor with the object of retarding this 
further swelling, for the effect of more salt would be to 
decrease the rate of tanning, after the manner about to 
be described. The presence of the chrome, moreover, will 
prevent too great swelling, for the hides receive a surface- 
tanning almost as soon as they are placed into the liquor. 

During the first hour or two in which the hides are 
in contact with the chrome-liquor, a greater number of 
acid-groups are removed from solution than chrome-groups. 
The basicity-value of the liquor is thus caused to rise at 
first. After this, however, and during the remainder of 
the tanning period, the relative absorption of the acid and 
chrome groups becomes reversed, i. e., more chrome than 
acid-groups are taken out of the liquor, the excess acid- 
groups then causing the "basicity" of the liquor to fall in 
value. Now, inasmuch as the rate of tanning is greater the 
more "basic" the chrome liquor, and vice versa, the effect 
of the increased acidity of the liquor as the tanning pro- 
ceeds is to slow up the tannage, and, finally, to stop It 
altogether. In order to allow tanning to proceed once 
more, then, the excess acid groups must be removed from 
solution by neutralizing them with alkali. In the first stage 



30 



NATURE AND CONTROL OF TANNERY PROCESSES 



of tanning, i. e., until tlie hides are "struck tlirough" by 
the chrome liquor, no alkali must be added to the liquor, 
else the insoluble chrome tanning compound thereby 
formed is deposited in the surface-layer of the hide, and 
this would prevent the entrance of the chrome-liquor into 
the interior of the hide. The addition of alkali to chrome 
tanning-liquors is, therefore, made about midway in the 
process, i. e., after the lapse of, say, the first twenty hours 
of paddle-tanning, or that of the first four hours of drum- 
tanning. 

In practise, the amount of alkali (which may be in the 
form of caustic soda, sodium carbonate, or sodium bicar- 
bonate,— preferably the latter) that is added to chrome 
tanning-liquors averages one per cent of the drained 
weight of the pickled goods. This quantity of alkali is dis- 
solved in water, and one of four or six equal portions of 
the solution is added to the tanning-liquor (which must be 
kept agitated) at an interval of every two hours, or of 
every hour. For rendering chrome tanning-liquors "basic," 
the ideal quantity of alkali is one which, when dissolved 
in the chrome-liquor exactly neutralizes the excess acid- 
groups released in tanning, and then brings the liquor al- 
most, but not quite, to the "precipitating-point," i. e., to 
the point at which the chromic sulfate in solution has com- 
bined with so many OH-groups as to have become nearly 
insoluble; for, tanning will proceed at the greatest rate (i. 
e., the fixation of chrome will be a maximum) when the 
liquor is almost, but not quite at the "precipitating-point." 

Now, the "precipitating-point" of a chrome-liquor Is 
quite independent of the basicity-value of the liquor; in 
fact, it bears but little relation to the "basicity" in the 
ordinary sense of this term. The "precipitating-point" — 
and, hence, the amount of alkali that must be used in order 
to approach this point— is controlled by at least five 
variables; these may be summed up as follows: 

(1) The concentration of the tanning-liquor. 

(2) The "basicity" of the liquor at the start of opera- 
tions. 

(3) The "basicity" of the liquor at the point the 
alkali is to be added. 

(4) The percentage of dissolved "neutral" salts in the 
liquor. 

(5) The temperature of the tanning-liquor. 

The concentration of the chrome-liquor affects the "pre- 
cipitating-point" by causing the chrome to precipitate out 
sooner the further the liquor is diluted. This is especially 
true of very "basic" liquors. The nature of this phenome- 
non is not perfectly understood, but may find explanation 
of a kind similar to that which accounts for the effect of 
"neutral" salts upon the action of chrome-liquors (see be- 
low). The difference between the initial and final basicity- 
values of the tanning-liquor — showing the extent to which 
the tannage has progressed — is a measure of the number 
of excess acid-groups released in solution; the greater this 
difference (i. e., the more excess acid-groups in solution), 
therefore, the more alkali will the liquor require. The 
presence of "neutral" salts in the chrome-liquor affects 
the "precipitating-point" in a very marked manner. With- 
out increasing the total acidity — in other words, without 
lowering the measurable basicity-value — of the liquor, 
yet in the presence of "neutral" salts, and in proportion 
thereto, more alkali will be required to bring the liquor 
to its "precipitating-point" than if no such salts were pres- 
ent. Wilson and Kern-" account for the effect of dissolved 



•The Ac 



:if Ne 



Upon Chroi 



Liqr 



•-Jour 



"neutral" salts upon chrome tanning, by stating that such 
salts become "hydrated" in solution (i. e., the salts attach 
to themselves, or combine with, a certain amount of 
water) ; by thus lessening the volume of water in which the 
acid-groups are dissolved, the effect of the salts is to In- 
crease the acid-concentration of the solution; the effect 
of more acid, then, is to make the use of a greater quan- 
tity of alkali necessary. The different "neutral" salts are, 
however, not all "hydrated" to the same extent; sodium 
sulfate, for example, has been found to combine with nearly 
twice the quantity of water that unites itself to sodium 
chloride, or common salt. To sum up, then, the effect of 
dissolved salts is to retard the tanning action of the 
chrome-liquors, and to make the use of comparatively 
"basic" chrome-liquors possible. Lastly, the influence of 
temperature upon the alkali-requirement of a chrome-liquor 
is simply a sequel to the "neutrar'-salts-effect; i. e., the 
higher the temperature of the tanning-liquor, the less the 
"hydration" of the salts, and the lower, therefore, the 
concentration of the acid-groups in the liquor. A warm 
chrome-liquor, being, in effect, more "basic" than a cold 
liquor, will, therefore, require less alkali to bring it to the 
"precipitating-point" than would the cold liquor. 

To the five variables referred to, another should be 
added, namely, that of the weight of the pickled goods 
entering the tanning-liquor. According to the weight of the 
pack, a greater or less amount of alkali will be required 
by the chrome-liquor, as more or less acid is introduced 
by the pickled hides. 

From what has been written, the fact will be apparent 
that chrome-tanning liquors can be completely exhausted, 
or deprived of their chrome-content, — in other words, all 
the dissolved chrome can be deposited in the hides, — if a 
sufficient quantity of alkali, added in small doses, and at 
the proper intervals during tanning be employed. Leather 
produced in this manner will, however, be of a soft and 
flexible (i. e., "stretchy") nature, resembling "two-bath"- 
tanned leather. Such a leather is not well-adapted for use 
in making shoe-uppers, for which a firm and "tight" leather 
is more to be preferred. Very "basic" liquors are also 
known to tan irregularly. Moreover, inasmuch as the 
swelling of hide, which — other things being equal — is 
known to take place, not only through the transverse di- 
mensions, but also throughout the length and breadth of 
the hide, the more "basic" the chrome-liquor is kept during 
tanning, the lower will be the yield of leather as measured 
by the surface area obtained. The foregoing considerations 
must, hence, be allowed to govern the amount of alkali 
that is to be used in tanning, and this, in practise, is kept 
very carefully regulated. 

Analytical Control. The procedure to be followed in 
the analytical control of the chrome-tanning process will 
depend on whether the "two-bath" process, or the "one- 
bath" process is being used. 

In "two-bath" tanning, an important requirement is 
the complete reduction of the chromic-acid absorbed by the 
goods from the first liquor. To test whether or not the 
chrome has been completely reduced, the spent liquor, or 
washings from the wet leather may be treated with dilute 
acid, potassium iodide, and starch, when a blue color will 
develop in the presence of unreduced chrome. The 
quantities of chrome absorbed by the goods, or conversely, 
those remaining in the spent-liquor, may also be deter- 
mined by any of the well-known methods. 

In "one-bath" tanning, each batch of stock chrome- 
liquor is, first of all, tested for 



NATURE AND CONTROL OF TANNERY PROCESSES 



31 



(1) The percentage of chrome, as Cr,0:,; 

(2) The percentage of acid, as SO3; 

(3) The basicity-value (found by dividing the percent- 
age of CnOj by that of the SO3) ; 

(4) Unreduced chrome (if the liquor was prepared in 
the tannery by the reduction of a dichromate-acid 
solution) ; 

(5) Tbe percentage of "free" sulfur (if the liquor 
was reduced with sodium thlosulfate, or "hypo.") 

From the percentage of chrome found by analysis may be 
calculated the number of pounds of chromic-oxide, or of 
sodium dichromate, present in every gallon of the liquor; 
on the basis of this value, then, the number of gallons of 
the liquor required in the tanning of a given weight of the 
pickled goods is measured out. Chrome stock-liquors con- 
taining unreduced chrome should not be used until such 
liquors have been treated with a further quantity of re- 
ducing-agent. 

The routine control of a "one-bath" chrome tanning- 
liquor in process should include the following determina- 
tions: viz., 

(1) That of the quantity of alkali required near the 
end of the tanning period to bring the liquor to 
its "precipitating-point"; 

(2) That of the basicity-value of the spent-liquor, and 
of the percentages of chrome and acid remaining 
in the liquor at the end of the tanning period. 

The quantity of alkali that must be added to the 
liquor to bring the latter to its "precipitating-point" is 
most readily determined by titrating a measured volume of 
the filtered liquor with an alkali-solution, until the "pre- 
cipitating-point" is caused to appear". A sample of the 
liquor is withdrawn from the paddle-vat or drum, treated 
with kaolin, and filtered through paper until perfectly 
clear; of the filtered liquor, an aliquot is measured out 
into a flat-bottomed glass dish, the latter placed upon a 
water-bath and heated until the liquor is of the same tem- 
perature as that of the liquor in the paddle-vat or drum; 
the dish is now supported upon a ring-stand placed over a 
white surface in such a position as to allow the entrance of 
light from a window through the sides and bottom of the 
dish; the standard alkali-solution, contained in a burette, is 
now slowly run into the liquor — which must be kept stirred 
— until the first appearance of a turbidity that remains per- 
manent is noted. The number of cubic centimeters of 
alkali-solution used is read off. and the number of pounds 
of alkali required by the liquor-contents of the paddle-vat 
or drum is then calculated on the basis of the known 
strength of the standard solution, and upon that of the 
gross volume of the tanning-liquor. The titration of the 
liquor should preferably be carried out with a pure caustic- 
soda or borax-solution, and not with a sodium-carbonate 
or bicarbonate-solution, even where the carbonate or bi- 
carbonate will be subsequently used for rendering the tan- 
ning-liquor "basic"; the reason caustic-soda or borax 
should be used for this purpose is that neither of these 
substances liberates carbon dioxide (CO2) during the titra- 
tion, the effect of carbon dioxide — acting in solution as an 
acid — being to delay the "precipitating-point" of the 
chrome-liquor beyond the point at which it should occur. 
The use of sodium carbonate, or bicarbonate, in the tan- 
ning-liquor, on the other hand, is to be preferred to that 
of caustic soda, for in this case, the presence of the car- 

-Douglas Mc- 



bon dioxide will act as a factor of safety in preventing the 
possible precipitation of a portion of the chrome in the 
vat-liquor to which the alkali is being added. 

The determination of the basicity-value of the spent 
chrome-liquor, and that of the percentages of chrome and 
acid remaining in the liquor at the end of the tanning 
period, are made to show the extent to which the tannage 
has progressed, as well as to furnish an indication of the 
quantity of chrome that is run to waste as each paddle-vat 
or drum is drained of its liquor. 

In addition to the foregoing determination, the meas- 
urement of the swelling power of a chrome-liquor may be 
made — as in the case of pickle-liquors— by means of the 
electro-metric method, and this will also show the rate of 
tanning of which the liquor is capable. 

The percentage of chrome absorbed and fixed by the 
hides during the usual process of "one-bath" paddle — or 
drum-tanning is about two-thirds of that initially present 
in the tanning-liquor. The remaining one-third is, more 
often than not, run to waste in the "spent" liquor, and as 
chrome is not an inexpensive substance, the money-loss 
resulting from this practice will amount to a considerable 
figure in the course of, say a year's operation. A3 in tho 
case of a pickle-liquor, however, it is quite practicable to 
restore a used chrome tanning-liquor to its original 
strength — merely by the addition of more stock-liquor,— 
and to use the same liquor repeatedly for, perhaps, ten or 
more packs of goods. Practical experiments in chrome 
paddle-tanning" conducted some time ago by the author 
of this paper have shown that the only variable diflScult 
of control in the replenishment of chrome liquors is the 
"neutral" salts-content of the liquors. Thus, during tan- 
ning, the percentage of common salt, and of Glauber's Salt 
in the liquor gradually rises, a greater quantity of these 
salts being always found in the spent-liquor than had been 
initially used in preparing the fresh liquor. Of course, on 
entering the pack of pickled goods into the chrome-liquor, 
the original salt-content of the latter becomes at once in- 
creased by several hundred pounds; inasmuch, however, as 
the hides undergo further swelling during tanning, in other 
words, since the amount of liquor absorbed by the goods 
is greater after tanning than it was before, it actually hap- 
pens that a portion of the salts used in preparing the tan- 
ning-liquor is removed therefrom by the pack of goods. The 
increase in the salt-content of the liquor after tanning is, 
therefore, not due to the salts transferred to it by the hides 
from the pickle-liquor, but is produced, in fact, (1) by the 
Glauber's Salt present in the stock chrome-liquor from 
which the tanning-liquor was made, and (2) by the alkali 
that is subsequently added for the pui'pose of rendering 
the liquor "basic"; in the latter case, the action of the acid 
in the tanning-liquor is to neutralize the alkali added 
thereto, and so produce a further quantity of Glauber's Salt. 
The Glauber's Salt thus added to a paddle-vat liquor during 
tanning will amount to, in practise, 75 or 100 pounds. By 
means of the above-described alkali-titration, however, it is 
possible, to a great extent, to counteract the effect of the 
increased salt-concentration of the replenished chrome- 
liquor, and merely by employing the amount of alkali indi- 
cated in the titration, to cause the replenished liquor to tan 
just as rapidly, and quite as uniformly, as a freshly-pre- 
pared chrome-liquor. 

The replenishment of a "one-bath" chrome tanning-liquor 
may be practised with entire success if the following 
means of control are adopted as a routine measure; viz.. 



32 



NATURE AND CONTROL OF TANNERY PROCESSES 




SOLVAY SODA 

For the Tanning Industry 

The Solvay Process Company — leaders in the manufacture of AlkaH since 1881 — with 
plants at Syracuse, N. Y., Detroit, Mich., and Hutchinson, Kansas and with warehouses 
at all leading shipping points, is in a position to serve the tanning industry in ALKALIES 
with superior quality and service. A staff of technical men who have studied the tan- 
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WING & EVANS, INC. 

Selling Agents for THE SOLVAY PROCESS CO. 

Address nearest office or distributor: 





MING & KVANS. IXC. 



THE DR.XCKETT CHKMIC.\L, CO. 



23 WilUam Street. New York, N. Y. 
30 N. Dearborn Street. Chicago, III. 
89 State Street, Boston, Mass. 
626 Book Building, Detroit, Mich. 
S31 Fonrth Avenue, Pittsburgh, Fa. 
Cincinnati, Ohio 
Cleveland, Ohi 



Syr 



N. Y. 



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Stocks carried at all principal shipping points. 




HEADQUARTERS FOR 



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'rniii;Hi¥M'iiiumdAiu 



NATURE AND CONTROL OF TANNERY PROCESSES 



33 



Before replenishing the spent-liquor, determine, 
by analysis, its chrome-content and basicity-value. 
On the basis of the chrome-content, add enough 
stock-liquor to restore the strength of the tanning- 
liquor to its original value; then, to the resulting 
liquor, add enough alkali to bring the basicity- 
value of the liquor up to its former point also. 
Perform the alkali-titration of the tanning-liquor 
in the usual manner, and at the proper time, and 



add to the liquor the amount of alkali indicated 
in the titration. 

After the passage of three or four packs of goods 
through the liquor, determine the specific gravity 
of the latter by means of an hydrometer. If the 
specific gravity is found to exceed 9° Baume, add 
enough water to the spent-liquor to reduce the 
reading to below 9°, determine the chrome-con- 
tent and basicity-value of the diluted liquor, and 
proceed as in (2). 



Method for Finding the Capacity of Tannery Paddle- Vats 
Tanks and Pits without Resorting to Measurements 



In routine control-work Involving the analysis of tan- 
nery-liquors, results are usually expressed in percentage 
by volume (e. g., in grains per one-hundred cubic centi- 
meters), or, less frequently. In percentage by weight (e. g., 
in grams per one-hundred grams, or pounds per one-hun- 
dred pounds). When the object is to compare the one 
liquor with another, this manner of expressing analytical 
results is the only one that allows of comparisons to be 
made. When, however, it is desired to replenish a given 
liquor in order that it may be used over again, or where 
the inventory-value of such a liquor is to be determined, it 
then becomes necessary to calculate from the analysis the 
total number of pounds that the liquor contains of lime, or 
salt, or acid, or chrome, — as the case may be. In order to 
arrive at these values, then, the gross volume of liquor 
that is being dealt with must be known, — in other words, 
the capacity in gallons or in pounds of the vat or drum 
holding the liquor must first be determined. In the case 
of square pits, or cylindrical drums or tanks having plane 
ends, it is, of course, a simple matter to find the volume 
or capacity of these, merely by obtaining certain dimen- 
sions of the vessel, and then multiplying these together. 
On account of the irregular shape of paddle-vats, however, 
the finding of their capacity by geometric means is a com- 
plex problem, involving the use of calculus. 

The following simple method has been devised by the 
author, and used by him with considerable success for the 
calibration — by analytical means, instead of by measure- 
ment — the liquor-contents of tannery paddle-vats. The first 
requirement is that the position of the water-line within 
the vat that is to be calibrated be fixed with respect to the 
height at which the vat, when placed into use, will be filled 
with liquor. Wooden strips marking the water-line are 
therefore nailed around the inside walls of the vat, and in 
all subsequent operations the volume of the liquor is kept 
constant by always bringing the latter to a level with the 
upper end of the wooden marking-strips referred to. The 
calibration of the vat is then performed in the following 
manner: The vat is filled with water to the level of the 
water-line, and a quantity (in the proportion of approxi- 
mately ten pounds to 2,000 gallons) of sulfuric acid (or any 
soluble acid, salt, or alkali, of known percentage purity, 



and whose recovery from solution may be quantitatively 
effected) is added, allowed to dissolve, and the solution 
thoroughly mixed by plunging it (say, for five minutes, by 
hand), or by other effective means. A sample (1) of the 
acid-liquor thus prepared is withdrawn and set aside. To 
the contents of the vat is now added a second portion of 
two or three times the quantity of acid originally given, 
this portion being, however, accurately weighed to within 
two per cent, the acid allowed to dissolve, and the liquor 
again thoroughly mixed; of the acid-solution in the vat, a 
second sample (2) is withdrawn and set aside. The second 
addition of acid is followed by a third of the same, or a 
larger quantity, the same degree of accuracy being ob- 
served in weighing, and a third sample (3) is taken of the 
acid-liquor in the vat. Fifty-cubic-centimeter aliquots of 
the different samples are now titrated with a tenth-normal 
alkali-solution, and the acid values thus found are ex- 
pressed in grams — 100 cubic-centimeters of sulfuric acid 
(HjSO.) present in each sample. The volume of the liquor 
in the vat is calculated in the following manner: 

Letting A, B and O equal the g/lOOcc of HjSO, found 

in samples (1), (2) and (3), respectively; 
and L', and L" the weight in pounds of sulfuric acid 
added to the liquor the second and third times, 
respectively; 
and P the percentage strength (correct to the first 
decimal) of the acid used; 

and G the volume in U. S., gallons of liquor in the 
vat; 
then, inasmuch as 11.983 g/lOOcc are equivalent to one- 
pound/gallon, 

G will equal L,' x P x 11.983 I: 
B— A 
or (check), 

G will equal L" x P x 11.983 II. 
C— B 

If the capacity of the vat thus obtained is found to be in 
the vicinity of 2,000 gallons, the results of equations I and 
II should check to within fifteen gallons, the accuracy of 
the foregoing method having been found to be 99.2 per cent. 



NATURE AND CONTROL OF TANNERY PROCESSES 



3^ 



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183 ESSEX ST., BOSTON 



NATURE AND CONTROL OF TANNERY PROCESSES 

Rctanning of Chrome Leather 



35 



The object of retanning chrome-leather is to complete 
the tanning of the goods. In the production of combination- 
tanned leather (i. e., of leather tanned with both chrome 
and vegetable materials), the purpose of retanning is two- 
fold; viz., 

(1) To complete the tannage, and 

(2) To impart to the resulting leather the appearance 
and character of vegetable-tanned leather. 

By reason of the peculiar nature of "one-bath" chrome- 
tannage, it is practically impossible to produce fully-tanned 
leather by this process without leaving the goods in con- 
tact with the liquor for an excessive length of time, or 
without the use of an excessive amount of alkali, the effect 
of which is to render the leather soft. Because of this ten- 
dency of a "one-bath" chrome-liquor to produce soft leather 
when caused to yield all of its chrome to the hide, such a 
liquor is never allowed to become completely exhausted 
during tanning. Instead, at the conclusion of the allotted 
period in which the goods are in contact with the liquor. 



the goods are moved into a fresh chrome-liquor, and al- 
lowed to absorb a further amount of chrome, the latter be- 
ing subsequently "fixed" by the use of alkali in the manner 
already described under "The Chrome Tanning Process." 

Chrome-retanning is unusually carried out in a drum 
by the use of a "one-bath" liquor, of which the percentage- 
strength is about one-half of that employed for the initial 
tanning-liquor. The quantity of alkali used is proportion- 
ately less, and the period of retanning is usually about one 
hour. 

After retanning, the wet leather is piled for a period of 
several days on the floor, the piles being covered with 
burlap for the puri)ose of preventing the goods from becom- 
ing dry. During the time in which the leather is left thus, 
the greater portion of the dissolved chrome in the liquor 
held by the goods will unite with the leather (i.e., the 
chrome will become "fixed"), the additional tannage thus 
produced (amounting, in practise, to about 70 per cent 
of the available chrome present) causing the absorbed 
liquor to become quite acid in reaction. 



'Neutralizing'' of Chrome Tanned Leather 



The final step of the "one-bath" chrome-tanning 
process consists in neutralising the excess acid released 
in tanning. The object of "neutralising" chrome-tanned 
leather, then, is 

ll) To render the chrome-substance deposited in the 
hide still more "basic", thus making the tannage 
quite stable and permanent; and 

(2) To prepare the leather for the subsequent fat- 
liquoring process by removing the excess acid 
referred to, together with the soluble chrome- 
salts remaining in the leather. 

The name "neutralisation," as applied to this final 
step of chrome-tanning, is a misnomer. The object in 
treating the chromed hides with alkaline solutions is not 
to neutralise the leather itself, but merely to reduce the 
"acidity" of the leather. "Neutralisation" is, therefore, a 
somewhat delicate operation; if carried too far, it would 
result in a portion of the chrome-substance in the hide 
being converted into chromic hydroxide, — a substance 
known to possess no tanning power. The foregoing cir- 
cumstance obviously excludes the use of any of the 
"stronger" alkalies, such as caustic soda, or even soda 
ash, in the neutralisation-treatment, for, even in very di- 
lute solution, any strong alkali would carry the neutralisa- 
tion of the surface of the leather too far before the interior 
was thoroughly penetrated. 

In practise, "neutralisation" of chrome-leather is ef- 
fected by the use of borax, or some equally mild alkali. The 
chromed hides are first washed in a drum with water, 
which serves to remove the greater portion of the acid and 
uncombined chrome-salts. The leather is then drummed in 
a one-half percent solution of the alkali (of which, in the 
case of borax, up to three per cent on the weight of the 
chromed stock may be given) until the desired degree of 
"neutralisation" is obtained. 

Probably the safest method of "neutralising" chrome- 



leather is that of Stiasny. of which method brief mention 
may here be made. In the method of Stiasny, the leather 
is paddled or drummed in a solution of ammonium sulfate 
(NHJ.SO.) and soda crystals (NaOH+Na,CO,). This is 
equivalent to, but cheaper than using a mixture of am- 
monium sulfate and ammonia, the soda in the former case 
reacting immediately with the ammonium salt and liberat- 
ing ammonia in accordance with the following equation: 

(NHj),SOj-!-2NaOH = 2NH,+Na.,SO,+2H..O. 

The ammonia thus set free combines with the excess 
acid in the leather, while the presence of the "neutral" 
salt Na^SO,, simultaneously formed, so reduces the already 
feeble dissociation of the ammonia, that by varying the 
concentration and proportion of these materials, the 
"neutralisation" may be exactly regulated to the required 
extent'". 

Analytical Control. The percentage of "free" acid 
remaining in the leather after "neutralising" may be deter- 
mined by digesting in water a weighed portion of the 
finely-divided leather, and titrating the resulting extract 
with a standard alkali-solution. Absolute results cannot, 
however, be obtained by any such method, for it must be 
remembered that the chrome-substance in the hide will 
continue to yield a portion of its combined acid so long as 
the leather is in contact with water. For control purposes, 
however, the results will be relative if the proportion of 
leather to water, the temperature of the latter, and the 
time of digestion be kept constant. 

A more accurate idea of the extent of the neutralisa- 
tion is obtained from the "basicity" of the chrome-sub- 
stance in the leather, found by determining the percent- 
ages of both chrome (as CnO;,) and total acid (as SO^) by 
the fusion method, and then dividing the one result by the 
other. 

In most cases it will be found sufficient to test for the 
-11. R. Profter.-Luc'. Cit. 



NATURE AND CONTROL OF TANNERY PROCESSES 




iiiiiiiiiiii;iiiiiiiiiiiiii{iiiiiiiiiiii!ii!iiiiiiiiiiiiiiiiii!niui!iiii 




ATISFACTORY fat-liquoring results are obtained 
only by using the best oils. 

We recommend any of the following materials as being 
particularly adapted to imparting to the leather those re- 
quirements most especially desired. 

Sulphonated Oils Moellon Degras 

Neatsfoot Oils Potash Soap 

Curriers' Greases 

SALEM OIL & GREASE CO. 

SALEM, MASS. 





ill nil iiiiiiiiiiiiiiir 



BASE -h FINISH = ? 

Let us help you with this problem 

First — Send us some pieces of your unfinished base, and, if possible. 
Second — Send us a finished piece of the color desired. 

We will send you the right finish to get the right results. 

TANNERS AND CURRIERS 
WHITTEMORE— WOODBURY'S 

COLORED PIGMENT FINISHES 

FOR GLAZING 

Pigment Finishes in the various Colors for CALF. SIDE. SHEEP and GOAT LEATHERS. 

Where a Glazed Finish is desired our Pigment Finishes are easily the best. 

We would be pleased to furnish samples. 

WHITTEMORE -WOODBURY CO. 

412 MEDFORD STREET, CHARLESTOWN, MASS. 



IP 



wmm 



NATURE AND CONTROL OF TANNERY PROCESSES 



37 



"degree" of acidity in the "neutralised" leather by deter- 
mining the reaction of the wash-liquor in which the "neu- 
tralisation" was effected. The spent liquor should in all 
cases show a neutral, or an acid reaction to methyl-orange 
indicator, showing that the neutralisation-treatment has 
not been carried too far. 

After the leather has been "neutralised." cuttings 
from the neck and butt portions are immersed in boiling 
water for a period of five minutes. If fully tanned, the 
leather will show no loss of pliability at the conclusion of 
the boiling period; if, on the other hand, the leather has 
been insufficiently tanned, the action of the boiling water 



will cause the cuttings to .shrink and curl up, and to be- 
come "horny" when dry. 

Chrome-leather should not be undertanned. The best 
chrome leathers contain from four to five per cent of 
chromic-oxide (CrjOj). Well-filled leather is obtained by 
keeping the chrome tanning-liquor as nearly neutral (i. e., 
as "basic") as possible. The more a leather is tanned, the 
more fat-liquor will it require, and the better will be the 
penetration. The heavier the leather is tanned, the less 
"stretch" will it give, and the more resistant to friction 
will it be ■■'°. 

nefects."— A. Seymour- Jones— Lentlief 



Trades Kev 



April 



11)15. 



The Fat Liquoring Process 



The purpose of fat-liquoring chrome-tanned leather is 
three-fold; namely, 

(1) To restore to the leather the oils or fats removed 
from the hide in the beamhouse processes, and 
thus to prevent the leather from becoming hard 
and "cracky" when dry; 

(2) To increase the tensile strength of the leather; 

(3) To render the leather wholly, or partially water- 
resistant. 

In the case of chrome-leather, the fact is well-known 
that before it has received a small quantity of oil, chrome- 
leather cannot be "wetted-back" again (i. e., the leather 
becomes water repellent) once it has been allowed to dry 
out. 

Fat-liquoring is merely a special form of applying oil 
to leather, the oil being given in the form of a water-emul- 
sion to the wet leather. The advantage of employing a 
water-emulsion of the oil, instead of applying the oil in its 
natural form to the dry leather, is that, in the former case, 
a small quantity of oil suffices to render the leather soft 
and flexible, while to produce the same effect with dry 
leather, a much greater quantity of oil would have to be 
applied. The reason that this is the case will be stated 
below. 

Pat-liquoring renders leather soft, and increases its 
tensile strength by lubricating and separating the fibres of 
the leather. The principal effect of the oil is, in fact, the 
separation of the fibres composing the leather, for it has 
been shown that the tensile strength of degreased leather, 
— while less than that of the leather with its fat-liquor 
left in. — is always greater than that of the leather before 
it has received any fat-liquor". Fat-liquoring, therefore, 
alters the fibrous structure of leather. The more oil in the 
form of fat-liquor that is incorporated with the leather, 
the more water-resistant, and the greater will be the ten- 
sile strength of the leather. 

All natural oils may be caused to emulsify (i. e., may 
be caused to mix with water) by several means. The first 
requirement is that the oil be broken up into small par- 
ticles (or, globules), which, in practise, is effected me- 
chanically by vigorous shaking or agitating. The "break- 
ingup" of the oil must be effected in the presence of an 
"emulsifying-agent," which may consist of any water-solu- 
ble colloid, such as 

" Thus, in the production of "patent" leather, the common 
practise is to degrease the le.nther after fat-liquoring, and before 
applying the varnish. 



(1) Gum acacia, gum tragacanth, "Tragasol," "Irish 
Moss," etc.; 

(2) Albumin, casein, or gelatin; 

(3) Sulfonated oil; 

(4) Soft, or hard soap; 

(5) Wool fat, or degras, 

of which the effect is to form a film around the oil-globules, 
and so prevent these from "running together" (or, coalesc- 
ing). Milk may be cited as a typical emulsion. In milk, 
butter-fat is held in water-suspension by the action of the 
dissolved casein, the casein preventing the fat-globules 
from rising to the surface. 

The readiness with which an oil may be "broken-up," 
or emulsified, depends principally upon its surface tension 
(i.e., upon the natui-al force which keeps the molecules 
composing liquids from repelling each other) ; the lower 
the surface tension of the oil, the more readily is it emulsi- 
fied, and the more permanent is the emulsion. Neatsfoot, 
linseed and olive oils are more easily emulsified, and form 
more stable emulsions than either castor oil or mineral 
oil, because, of the oils in the first-named group, the sur- 
face tension is only about one-half of that of castor oil or 
mineral oil. True emulsions are characterised as being 
more viscous (i. e., less "fluid") than the oils from which 
they are made. Emulsified oils penetrate wet leather more 
uniformly, and are absorbed more rapidly than natural oils 
are absorbed by dry leather, because the surface tension 
between oil and water is less than that between oil and 
air. Just as the oil having the lower surface tension emul- 
sifies the more readily (i. e., produces the finer particles), 
so will such an oil penetrate wet leather most rapidly. The 
effect of increased temperature is that of lowering the 
surface tension of oils; hence, the higher the temperature 
employed in the fat-liquoring process, the more uniform 
and rapid will be the absorption of the oil by the leather. 

In general, the oils most suitable for treating leather 
are those of the "semi-drying," or "non-drying" variety (i. 
e., oils which do not tend to harden or solidify on exposure 
to air). Oils of the "semi-drying" variety are castor, neats- 
foot, and olive; of the "non-drying" oils, ordinary mineral, 
or paraffin oil is an example. Fish (e. g., cod or menhaden) 
oils belong to the class of "drying" oils; the latter, — being 
subject to atmospheric oxidation and hardening, — are, for 
this reason, not so well adapted as the oils in the first- 
named groups for the purpose of softening and nourish- 
ing leather. The disadvantage of neatsfoot oil is that — 



38 



NATURE AND CONTROL OF TANNERY PROCESSES 



THE LIQUOR IN YOUR CELLAR 

In the fat liquor Drum hangs the fate of your 
leathers. 

Good mellow leather, soft, evenly penetrated, 
bright colors, and perfect gloss, absolutely free from 
grease, gum and spue come from using our specially 
treated oils and fat liquors instead of the ordinary kind. 

For 25 years tanners have depended on them, and 
competitors have vainly tried to make something as good 
as our TREATED COD OILS and TREATED NEATS- 
FOOT OILS, which run ABSOLUTELY UNIFORM. 

Write us that you are interested in getting better 
results, and in saving time and money. Ask us to send 
literature, samples or salesman — Which? 

SECCOMB-KEHEW- BRADLEY COMPANY 




Office 

10 Post Office Sq. 

Boston 



Established 1854 



Factory 

Maiden, 

Mass. 



SULPHONATED OILS 

CASTOR AND COD 

FAT LIQUORS 

BLENDED TO MEET EVERY REQUIREMENT 

JOHN SHAW & CO. 

Manufacturing Chemists 
15 ELKINS STREET - - - - SO. BOSTON, MASS. 

ESTABLISHED ISfiO 



NATURE AND CONTROL OF TANNERY PROCESSES 



unless very carefully "col(l-presseci"~it tends to form 
"spue" on the surface of the finished leather with which 
it is incorporated. Mineral, or paraffin oils are quite inert 
substances; while lacking the nourishing and filling prop- 
erties of castor, neatsfoot, and olive oils, mineral oils may, 
however, be freely and safely employed in the f:il-li(ninriiis 
of leather, provided, always, they can first be brought into 
the form of a stable emulsion. For use in fat-liquor, 
preference should be given to the heavier grades of min- 
eral oil (e. g., those having specific gravities at 60° Fahren- 
heit of .88 to .92); on account of the fact that the lighter 
mineral oils are more or less volatile (i. e., tending to 
evaporate) at ordinary temperatures, the use of these is 
best confined to the "oiling-off" of the grain-surface pre- 
paratory to the glazing of the finished leather. 

Degras is the oxidation-product of cod-liver oil, formed 
in the "chamoising" of sheep-skins, while wool-fat, or cnide 
lanolin, is a natural wax extracted from raw wool. From 
crude wool-fat is obtained, by distillation, a liquid wax 
known as "oleine." The emulsifying property of these 
substances is shown by their capacity to mix with large 
volumes of water. In addition, however, to being excel- 
lent oil-emulsifiers, degras, wool-fat, and oleine possess in 
themselves filling and nourishing qualities in a high de- 
gree when used upon leather in the form of fat-liquor, 
either alone, or in combination with one or more of the 
natural oils. 

Within very narrow limits only does the color of the 
oil, or oils used in the fat-liquoring process determine the 
color of the leather. The color which the fat-liquored 
leather will assume depends on the amount of oil that is 
left in the surface-layer of the leather; in other words, the 
better the penetration of the fat-liquor into the interior, 
the lighter will be the color of the leather, and vice versa. 
Of the different emulsifying-agents cited above, the 
effect of water-soluble gums and protein-substances (see 
1, and 2 in the list) is not only to form a protective coat- 
ing around the oil-globules, but also to counteract the up- 
ward movement of the oil-globules due to the force of 
gravity. Gums and proteins, however, have the disadvan- 
tage of decomposing In solution rather easily, and for this 
reason, are seldom employed as oil-emulsifiers. Modern 
fat-liquors, on the other hand, are of two kinds: namely, 
"acid fat-liquors," and "alkaline fat-liquors." "Acid" fat- 
liquors are those prepared with sulfonated oils, while "alka- 
line" fat-liquors are made from ^oap, wool-fat, or degras. 
The emulsifient used in preparing "acid" fat-liquors, name- 
ly, sulfonated oil, is made by treating any fatty oil, such 
as castor, corn, neatsfoot, or fish oil, with concentrated sul- 
furic acid, the effect of the acid being to convert a portion 
of the oil into its sulfo-fatty acid; the sulfo-fatty acid thus 
produced forms the emulsifying principle of the sulfonated 
oil, enabling the latter to mix with water, and to carry along 
with it into solution other natural oils with which it may 
be incorporated. Properly^made "acid" fat-liquors are sel- 
dom, if ever, more than faintly acid in reaction; more 
often than not they are quite "neutral," and may even show 
an alkaline reaction. On account of the fact, however, 
that by nature they are inclined to be "acid", sulfonated 
oils are particularly well-adapted to the fat-liquoring of 
chrome-leather, which, when wet, is always slightly "acid" 
by nature. On the other hand, the nearer the reaction of 
the "acid" fat-liquor approaches neutrality, the lower will 
be the surface tension of the oil, and the better, therefore, 
will the fat-liquor be enabled to penetrate the leather with 
which it is in contact. "Alkaline" fat-liquors, having soft 



or hard soap as their base, and often containing wool- 
fat, degras, or moellon, are, as a rule, much heavier (i. 
e., more viscous) in body than "acid" fat-liquors. The sim- 
plest way to make an "alkaline" fat-liquor is to heat any 
fatty oil, and then to stir into it a very small quantity of 
caustic potash (sufficient to saponify only a small portion 
of the oil) dissolved in water, and after this to add warm 
water until the emulsion is of the desired consistency. 
This method of preparing an "alkaline" fat-liquor is, of 
course, equivalent to that in which the oil is added in a 
fine stream to a hot soap solution, the product obtained 
in either case being quite the same. The quantity of soap 
used in making "alkaline" fat-liquors should be just suffi- 
cient to produce a stable emulsion with the oil. A correct 
proportion of soap will impart to the leather a feeling of 
"fulness" not obtained without the use of soap, while an 
excess of soap will produce a leather that is difficult to 
finish. In the preparation of "alkaline" fat-liquors, pot- 
ash, or soft soap, finds preference over soda, or hard soap, 
for two reasons: viz.,, first, potash soap is a more power- 
ful oil-emulsifient than soda soap; secondly, the use of pot- 
ash soap permits the leather to be afterwards glazed, while 
hard soap— on account of its action in cementing together 
the fibres of the leather — renders glazing difficult, and is 
quite apt to produce "flat" and dull-appearing leather. By 
reason of the fact that "alkaline" fat-liquors produce a 
greater degree of "fulness" than "acid" fat-liquors, the 
former are extensively used in the fat-liquoring: of chrome 
and combination-tanned split leathers, while "acid" fat- 
liquors find their principal application in the production of 
the more closely-grained shoe-upper leathers. 

Inasmuch as salts, in general, interfere with the fat- 
liquoring treatment (causing the oil-emulsion to break up), 
chrome leather should invariably be washed after being 
"neutralised," and immediately before it is fat-liquored. The 
washing of the leather is carried out in a drum with warm 
water (at 120° to 140° Fahrenheit), and lasts for a period 
of fifteen to thirty minutes, or until the goods are free 
from salts. After the washing of the goods the wash-water is 
run off, sufficient fresh water at 130° Fahrenheit to sub- 
merge the leather is run into the drum, the latter set into 
motion, and the warm fat-liquor then fed through the hol- 
low axle to the contents of the drum. By thus conducting 
the washing and the fat-liquoring in a single drum, the 
goods will be of the proper temperature to receive the fat- 
liquor when this is added, and the necessity of heating the 
drum prior to fat-liquoring is hence avoided. 

In order to insure success, the following points must 
be observed in the "acid"-fat-liquoring of chrome-tanned 
leather: viz., 

(1) that neither the wet leather nor the fatliquor is 
more than faintly acid in reaction; 

(2) that the temperature during the fat-liquoring 
treatment is 130° Fahrenheit or higher; 

(3) that a sufficient quantity of water be used to 
allow a portion of it to remain in the drum at the 
conclusion of the treatment. 

AVhen insufficiently neutralised, chrome leather is fat- 
liquored, the oil-emulsion will not penetrate, but, instead, 
the excess acid in the leather will cause a "splitting-up" 
of (i. e., liberation of the fatty acids in) the oil; thus, in 
place of the oil being deijosited within the interior, the 



40 



NATURE AND CONTROL OF TANNERY PROCESSES 



DYESTUFFS FOR LEATHER 

Present day fashions demand from the Tanner a wide range of shades, which are 
constantly fluctuating in popular favor. In view of this fact, — a Tanner must 
necessarily have a wide range of Dyestuffs and Formulae at his command. 
Furthermore, he must have the assurance that the Dyestuff is the RIGHT DYE- 
STUFF— both in QUALITY and PRICE. He should be confident that every lot 
he puts through will be identical with the preceding one. Standardization means 
SALES— CONFIDENCE. 

Bearing this in mind we offer the Tanning industry a complete line of ACID, 
BASIC and DIRECT COLORS. In addition we offer our long experience in 
Leather coloring; our laboratories and technical assistance; and a degree of serv- 
ice that is unsurpassed. 



Your problems are oi 



93 Broad Street 

Factories 

Ashland, Mass. 
'>:^: Garfield, N. J. 



)licit your inquiries. 



D. J. LARKIN CO. 



Boston 3, Msiss. 

Selling Agents 

Henry Woods Sons Co. 
Wellesley, Mass. 



H. S. P. 

UNIFORM FINISH 

A Superior Pigment Finish 
IN ALL COLORS FOR 

KID, CALF 
SIDE, SHEEP 

For years we have been supplying the tanners 
at home and abroad with high grade products 
and unequalled service. 

OUR VULCAN FAT LIQUORS ARE 

SUPERIOR TO ANY ON THE 

MARKET 

CHEMICAL RESEARCH CO. 

Office and Factory Branches 

652 SUMMER ST. 



LYNN, MASS. 



ST. LOUIS 
CHICAGO 



SULPHONATED OILS 

COD MOELLON 

NEATSFOOT BLOWN OILS 

CASTOR OIL SOAPS 

CORN 

The Oil & Chemical Corporation 

Refiners and Manufacturers of animal, vegetable 
and petroleum oils. 

4600-4650 Iowa Street, Ch-cago 





VICTOR J. POLL « CO. 








Estabiisiioa :nii 




SULTAN 


SULPHONATED 


OILS 




Moe 


Ion Degras Extracts 




163 W. 


AUSTIN 


AVE. CHICAGO 



Shoe and Leather Reporter Directory 
of Shoe Manufacturers for 1922 

READY FOR YOU! 



NATURE AND CONTROL OF TANNERY PROCESSES 



41 



fatty acids will remain on the surface of the leather in the 
form of "spue." In order to counteract the acid-reaction 
of a sulfonated-oil fat-liquor, a small quantity of aqua am- 
monia is commonly added to the liquor before it is fed 
to the drum. The effect of temperature upon oil-emulsions 
has already been described; the fact may be stated here 
that a large percentage of failures are due to the use of 
too low temperatures in the fat-liquoring treatment. With 
chrome leather, temperatures up to 160° Fahrenheit may 
safely be employed. The volume of fat-liquor in contact 
with the leather must be large enough to enable the fat- 
liquor to reach all parts of the leather, and to allow the 
oil-emulsion to penetrate completely. Dark sjjots appear- 
ing in the finished goods are due to excess oil on the sur- 
face, the fat-liquor not having been absorbed by reason 
of employing an insufficient volume of water, or because 
the temperature during the lat-liquoring process was kept 
at too low a point. 

On account of the difficulty in obtaining even coloring 
of fat-liquored leather, leather which is to be finished with- 
out the use of pigments is usually dyed before it is fat- 
liquored. When dyed leather is to be fat-liquored, the vol- 
ume of the liquor is kept as small as possible in order to 
prevent excessive "bleeding," or stripping of the color 
from the goods. "Bleeding" of the color may, however, be 
checked by the addition to the fat-liquor of a suitable quan- 
tity of dye™. When employed upon dyed leather, the fat- 
liquor should be made as nearly neutral in reaction as 
possible. 

The proper quantity of oil for use upon chrome leather 
depends on the purpose to which the leather will be put in 
service, and, in practise, will vary between rather wide 
limits. Shoe-upper leather, for instance, may contain any- 
where from three to 15 per cent of oil, the lower limit be- 
ing for leathers that are to receive a high polish, such as 
kip and side, the higher values for the softer kid, and so- 
called "elk" leathers. In all cases where the leather is to 
be glazed or polished, an excessive amount of oil is to be 
avoided. Where it happens that — due to too much oil in 
the surface-layer — the leather will not glaze, the leather 
may first be brushed over with a dilute solution of formic, 
acetic, or lactic acid, after which the goods will usually be 
found to glaze quite readily. Lack of enough oil in the 
finished leather is not always responsible for the "crack- 
ing" of the grain so often observed in the case of shoe- 
leathers that have been in warehouse storage for a period 
of some months. "Cracking" of the grain is quite fre- 
quently the result of loss of moisture which leather stored 
in a dry or heated atmosphere suffers; in order, therefore, 
to prevent the grain thereon from cracking, leather must 
be preserved in a cool place where the atmosphere is not 
too dry. 

Analytical Control. Inasmuch as, in the fat-liquoring 
process, practically the entire quantity of oil fed to the 
leather becomes absorbed by it, the process itself will re- 
quire but little control of an analytical nature. The an- 
alytical work in connection with fat-liquoring is, therefore, 
confined to the testing of the raw materials (viz., the nat- 
ural oils employed, sulfonated oil, degras, sod-oil, wool-fat. 
soap, etc.) which enter into the preparation of the fat- 
liquors, and to that of the condition of the leather that is 
to be fat-liquored. 

The examination of the natural oils should include 
such determinations as specific gravity, degree of cold- 
test, acid-number, iodine-number, and quantity of unsaponi- 
■■' Acporrting to the suggestion of M. C. Lamb. 



fiable oil present. The specific gravity and iodine-number 
usually serve to identify the oil under examination, while 
the presence of over five per cent of unsaponifiable oil will 
indicate admixture with mineral oil, wool-oil, or sperm-oil. 
The iodine-number (i. e., the percentage of iodine that the 
oil is capable of absorbing), moreover, measures the "dry- 
ing-power" of the oil; thus, the iodine-number of "non- 
drying" oils will range from zero to 65; that of "semi- 
drying" oils, from 65 to 120; while the iodine-number of 
"drying" oils will vaiy from 120 or 130, in the case of the 
fish oils, to 180, which is that of linseed oil. The degree 
of cold-test (i. e., the temperature at which the oil becomes 
solid) is indicative of the solid fatty-acid (e. g., stearin) 
content of the oil; thus, for example, the more stearin an 
oil contains, the higher will be the temperature at which 
the oil will freeze or become solid, and the more apt such 
an oil would be to form "spue" upon leather. The acid- 
number of natural oils is equivalent to the percentage 
of "free" fatty-acids present. A freshly-expressed oil will 
show a very low acid-number (e. g., not over 5), but as 
the oil is exposed to the action of moisture, air, and light, 
the acid-number will increase, and may reach the figure 
50 in the case of such products as degras and moellon. A 
high acid-number does not necessarily indicate "rancidity" 
of the oil; since "rancidity" is produced, however, by at- 
mospheric oxidation, any increase in the acid-number of 
the oil usually means a corresponding increase in the 
"rancidity." In the fat-liquoring of leather, "free" fatty 
acids must be considered an advantage, insofar as they 
help to emulsify the oil; the excellent emulsifient proper- 
ties of degras and moellon, for example, are in part thus 
due to the high content of free fatty-acids possessed by 
these materials. Finally, it should be explained that a 
high percentage of unsaponifiable oil occurring in the oil 
under examination may not always represent so much 
mineral oil; thus, unsaponifiable oil may consist of liquid 
waxes (of the type of wool-oil, or "oleine") which, in com- 
bination with sulfonated oil, as a rule, yield fat-liquors of 
a very high grade. 

The analysis of sulfonated oils is made to determine 
the percentages present of water, ash, admixed unsaponifi- 
able oil, if any, and combined sulfuric acid as (SO3). Sul- 
fonated oils, as a rule, contain from 20 to 25 per cent of 
water. The percentage of ash will vary from 1.5 or less 
in the case of sulfonated oils neutralized with ammonia, to 
5 or 6 in the case of oils finished with soda. The per- 
centage of combined SO;, — found by determining the per- 
centage of total SO;., and subtracting from this that of the 
SO3 present as Glauber's Salt — will indicate the degree of 
sulfonation to which the oil was subjected in the process 
of its manufacture; it varies from one per cent in the case 
of lightly-sulfonated oils, to five per cent in that of the 
highly sulfonated oils. In order to compare the sulfona- 
tion-values of two sulfonated oils, it will be necessary to 
first calculate their percentages of combined SO,, on the 
basis of the quantity of total fatty oil present in either oil. 

The degras, or moellon, that is to be used upon leather 
is first tested for melting-point, and for the percentages 
present of water, ash, unsaponifiable oil, "free" fatty-acids 
(i. e., acid-number), and oxidized fatty-acids. Degras will 
contain up to 15 per cent of oxidized fatty-actds; the latter 
substances possess a great affinity for leather, combining 
with it to produce a sort of additional tannage, and are 
hence considered a very valuable adjunct to the fat-liquor- 
ing treatment. Sod-oil is an inferior grade of degras, 
showing, as a rule, tree mineral acid, and a high percentage 
of ash; these arise from the sulfuric-aeid and lye-treat- 



NATURE AND CONTROL OF TANNERY PROCESSES 



OUR NEW TRADE MARK 



Nomad Products 




Nomad Degras. 

Nomad Paddle Oil. 

Nomad Pure Moellon Degras, 

Nomad Olive Fig Soap. No. 1. Guaranteed 
Pure Potash. 

Nomad Fig Soap No. 50. 

Nomad W. Sulphonated Ceistor Oil especially prepared for white leathers. 

Nomad A. Sulphonated Newfoundland Cod Oil especially prepared for Chrome 
upper leather. 

Nomad S. Sulphonated Newfoundland Cod Oil for upper and sole leather, bark 
and chrome splits. 

Nomad Guaranteed Pure Newfoundland Cod Oil. 

FRED W. DAMON 

214 PURCHASE ST. BOSTON, U. S. A. 




NATURE AND CONTROL OF TANNERY PROCESSES 



43 



ments which sod-oils receive in the course of their manu- 
facture. Commercial degras and sod-oils are usually ad- 
mixed with natural oils and tallow, which must hardly be 
regarded as adulterants. Degras and sod-oil, however, 
often contain mineral oil and wool-grease, which, if present, 
will be found in the unsaponifiable portion extracted from 
the former substances. 

Soaps used in the preparation of "allialine" fat-liquors 



should contain no "neutral" salts, inasmuch as the latter 
tend to break up oil-emulsions in general. The nature of 
the fat or oil (i. e., whether a solid or a liquid fat), and 
that of the alkali (i. e., whether soda or potash) of which 
the soap was made may be determined by chemical an- 
alysis. The analysis of soap may also include the deter- 
mination of the water-content, and that of the presence or 
absence of rosin, filler, and free caustic alkali. 



NATURE AND CONTROL OF TANNERY PROCESSES 




In this color card are exhibited 54 dyeings, showing Acid and 
Basic Dyes on samples of Sumac-Tanned Sheepskin, and a 
.omplete range of Mode Shades on Chrome-Tanned Calf- 
skin. 



Dyes for Leather 



M 



OST tanners know the advantages of using "National" dyes, 
either in brush or paddle dyeings on vegetable tannages for drum 
dyeings on chrome-tanned leather. 



A full range of colors is obtainable. These extend from the 
bright shades produced by "National" acid and basic dyes on vegeta- 
ble-tanned skins to the popular browns, cordovans, grays and blacks 
on chrome-tanned skins. 

"National" leather dyes possess the valuable properties of easy 
application, brightness, fastness and evenness of shade. 

The illustration above shows the latest color card issued for the 
use of tanners and leather manufacturers. A copy will be gladly sent 
upon application. 



National Aniline and 



COeo, Inc. 



New York 
Boston 
Chicago 
Hartford 
Charlotte 







Montreal 
Toronto 
Providence 
Philadelphia 
San Francisco 



NATIONAL DYES 



NATURE AND CONTROL OF TANNERY PROCESSES 
Appendix to Nature and Control of Tannery Processes 



Tile C'olorinc of Leather. 



The Coloring of Leather 



LEATHER is colored with dye woods, coal tar dye- 
stuffs or pigments. The most important dye woods 
used are logwood, fustic and hypernic. Besides pos- 
sessing a high degree of coloring properties, these dye 
woods have tanning qualities and also mordanting proper- 
ties for basic dyes. 

Many vegetable tanning agents which are used to give 
the grain of the leather some particular quality, or to fill 
the fibres of the leatlier, also have some slight dyeing 
properties, but are more generally used as mordants for 
the basic dyes. The most important method of dyeing 
leather, however, is by the use of coal tar dyes, and these 
are usually considered under the following divisions; 
Basic dyestuffs Alizarine or mordant dyestuffs 

Acid dyestuffs Sulfur dyestuffs 

Direct dyestuffs Dyestuffs diazotised and de- 

Dyestuffs oxidized on fibre veloped on fibre 

Dyestuffs commonly known as vat colors, such, for ex- 
ample, as indigo, are not suitable for leather. 

BASIC DYESTUFFS are most commonly used be- 
cause leather was formerly made almost entirely with 
vegetable tanning materials. These colors are also suita- 
ble for chrome leather, after it has been properly mor- 
danted with a vegetable tanning material. 

Basic dyes are best dissolved by mixing them thor- 
oughly with cold water and then raising the solution to 
nearly a boil with a steam jet. Cold water is most advan- 
tageously used because basic dyes frequently contain ma- 
terial which is likely to cake if the dyes are put into hot 
■water. Auramine, for instance, should not be dissolved in 
water over 175° P. If the water is hard the basic dyes 
should be wet with one-half their weight of acetic acid 
Ijefore the water is added. Phosphines which are not af- 
fected by the hardness of the water may be dissolved with- 
out the addition of acetic acid, even in very hard water. 
Dyes were formerly made by the purification of a by- 
product of magenta, but the new phosphines, such as phos- 
phine G N, are made synthetically and are much purer 
compounds. 

Basic dyes as a class are not very fast to light, and in 
this respect many acid, direct and alizarine dyes are su- 
perior to basic dyes. It should be remembered that it is 
practically impossible for the dyer of leather to secure 
such excellent results as are possible for the textile dyer, 
because the tanner cannot boil the leather. National Phos- 
phine G N, Bismarck Brown 53, Safranine A, Methyl Blue 
BD and New Blue D A cone, are faster to light. National 
Auramine O, Chrysoidine Y Ex. and 3T, Fuchsine N B Cry. 
Methyline Violet 2B and Victoria Green W. B. Cry. pos- 
sess the greatest penetrating qualities of the basic dyes. 

Basic dyes are much improved in their fastness to fat 
liquor and finishing if they are after-treated with tartar 
emetic, potassium titanium oxalate or bichromate of pot- 
ash. These salts also give more level results with basic 
dyes if the bottom is fixed with them before dyeing. 

ACID DYES are used on all kinds of tannages. They 
readily dissolve in hot water and do not require a mor- 
dant. The depth of color obtained by their use is much 
improved by the addition of sulfuric or formic acid to the 
dye bath. Best results are obtained by adding the acid 
towards the end of the dyeing operation. The use of an 



acid is, however, undesirable, especially on chrome leather, 
if after dyeing the leather has to be fat liquored with an 
alkaline emulsion of oils, because the acid is liable to cause 
grease spots by curdling of the fat liquor. 

Whenever acid is used the leather should be thor- 
oughly washed afterwards. Some of the best levelling acid 
dyes are National Wool Yellow EX Con. Wool Orange A 
Cone; Wool Orange GG Cry., Fast Crimson G R, Fast 
Crimson 8 B L, Alphazurine 2 G, Alizarin© Sapphire F S, 
and Acid Fast Violet B G. 

These colors are reasonably fast to light and are also 
easily dissolved, which causes them to penetrate the 
leather and to produce very level shades. 

They are excellent for making light pearl and ecru 
shades, but are not suitable for dark shades. Acid colors 
which are in the most common use are National Metanil 
Yellow 1955, Azo Yellow A5W, Resorcine Brown R and 
R W, Wool Scarlet B R, Croceine Scarlet MOO, Fast Red 
S Cone. Acid Bordeaux, Wool Violet 4 BN, Pure Soluble 
Blue, Induline N T, Durol Blue H R, Buffalo Black N B R, 
Buffalo Black A R, Acid Green L Cone, and Nigrosines. 

The most important of these colors for leather dyeing 
is the line of Nigrosines which is used to produce blue- 
blacks on vegetable and chrome tanned leather and for 
making black seasons for finishing leather and for black- 
ings and shoe polishes. The Nigrosines most commonly 
used for dyeing leather are: 

National Nigrosine 128 (bluish) 
National Nigrosine 27722 (greenish jet) 

Those used for seasonings and blackings: 
National Nigrosine 2011 cone, (bluish) 
National Nigrosine 4523 cone, (jet) 
National Nigrosine 3099 cone, (greenish jet) 

Those Nigrosines which are ammonia proof are: 
NationaKNigrosine 51457 (bluish) 
National Nigrosine 19903 (bluish black) 

There is also to be considered Spirit Nigrosine SG, 
which is soluble in alcohol, but not soluble in water, and 
which is related to the above nigrosines. 

Acid dyes are used extensively on vegetable and 
chrome tanned leather as a bottom for basic dyes which 
are precipitated by the acid dyes and produce full level 
colors. Their greatest usefulness in fancy shades has 
been to produce brown glazed kid where they are used 
on chrome tanned goat skins, bottomed with fustic and 
logwood. 

Acid dyes are not firmly fixed on leather by any proc- 
ess; they have a tendency to bleed off in the fat liquor, 
wherein lies one of the greatest objections to their use. 

DIRECT DYES have created an important place for 
themselves in the dyeing of chrome leather. They attach 
themselves directly on to this material without any mor- 
dant, but they have only a slight affinity for vegetable 
leather. For this reason they give better results on chrome 
leather after it has not been retanned with any vegetable 
tanning agent. 

There are, however, some direct dyes which are suit- 
able for producing very light and level shades on vegetable 
tanned leather. 

Direct dyes are readily soluble in water and, unlike 



46 



NATURE AND CONTROL OF TANNERY PROCESSES 



American Dyewood Dyes 
for Leather 



For hides properly tanned, it is only necessary to use 
dye-stuffs of proven value to secure maximum service 
in any leather. 

WE RECOMMEND 

Logwood Extracts, Hematine Pastes and Crystals, Hy- 
pernic Limawood and Redwood Extracts, Fustic Extracts, 
Persian Berry Extracts, Ground Turmeric, Gambler 
Paste and Sumac Extract. 

The qualifications of the above dyestuffs on chrome 
tanned leather are as follows: 

1. They penetrate thoroughly; 

2. They dye absolutely level; 

3. They produce a mild tanning action; 

4. They improve the feel and strength of the grain; 

5. In consequence of the above, they are applied to 
give the necessary grounding for aniline colors 
so that uniform shades may be produced with 
regularity. 



FOR DYEING AND FINISHING, WE RECOMMEND 

Russett Phosphine for tan base, Russett Brown for dark 
and brown base; Russett Mahogany; Russett Red for 
Russia red base; Ebonite for blacks; etc., etc. 

For Other Shades 
Write for Leather Shade Cards 



Liquid Extracts sold in barrels of 500-550 lbs. Crystals 
Extracts sold in boxes of various sizes. 25-60 lbs. Alsi 



old in barrels of .350-400 lbs. Solid 
in special weights as ordered. 



AMERICAN 

Dyewood Company 



New York — Boston — Philadelphia — Hamilton, Ont. 
Works at Chester, Pa. 



NATURE AND CONTROL OF TANNERY PROCESSES 



4T 



basic dyes, they are less soluble in acid solutions 
and become more soluble when an alkali is added 
to the dye bath. Because of this characteristic, 
chrome leather should be as nearly neutral as pos- 
sible before dyeing, in order to secure the most level 
results, and it is not necessary that the dye bath should 
be acidified, even at the end of the dyeing operation, as the 
colors exhaust completely unless there is an undue excess 
of the dyestuff. 

Direct colors most suitable for chrome tanned leather 
are: 

National Erie Fast Yellow WB 
" Yellow Y 
" Orange CG 
" Fast Orange A 
" Scarlet 8 BA 
'■ RedFD 
Niagara Sky Blue 6 B 
Diazine Black H. Ex. 
Erie Black GXOO 
Direct dyes are often improved in respect to their 
fastness to fat liquor by after treatment with bichromate 
of potash or copper sulphate. They seem, however, to be 
affected detrimentally by iron salts. Some direct dyes 
work better in the dye bath if 2-3% of salt is used. Na- 
tional Erie Black GXOO is the most important of the di- 
rect colors used by leather manufacturers. It has come 
into successful competition with logwood and Nigrosine 
on chrome leather. It does not yield a black as cheaply 
as logwood, but on the other hand it does not make the 
leather as tender or as harsh feeling as logwood. National 
Erie Black GXOO does not bleed in the tat liquor as much 
as Nigrosine. If it is used in connection with logwood, it 
should be dyed on the leather before the logwood, in order 
to give the deepest black result. A good black on chrome 
leather is obtained by dyeing the neutralized leather as 
follow.<v: 

For 100 lbs. wet weight, work for twenty min- 
utes at 120° F. with 12 oz. National Erie Black 
GXOO, then for twenty minutes at 120° F. with 1 
lb. of logwood crystals, 2 oz. bicarbonate of soda. 
Fix for ten minutes at 100° F. with 2 oz. of cop- 
peras. The material is then fat liquored in the 
usual manner. 

The direct dyes give excellent colors on chrome 
leather which can be finished without glazing on the grain 
or on chrome leather finished in ooze. They are much 
faster to light than basic dyes. When topped with basic 
dyes they produce colors which are fairly fast to light, and 
have the fullness and brightness of the basic dyes them- 
selves. 

ALIZARINE OR MORDANT DYES have been used to 
some extent on chrome leather, as they are the fastest 
colors to light which are known. Many of this class of 
dyes, however, are unsuitable for general use, because the 
full value of the color is not developed except at a boiling 
temperature. For instance. Alizarine Red is actually yel- 
low until it is developed by chrome at a boiling tempera- 
ture. Different chemicals, such as bichromate of potash 
and potassium titanium oxalate, have been proposed as 
substitutes for a boiling temperature, but they have been 
only partially successful. There are some mordant colors, 
however, which develop cold, while others give shades which 
are useful although undeveloped. These colors as a class are 
usually dull and are much improved if topped with basic 
dyes. National Superchrome Yellow B N is the most im- 
portant mordant dye. 



Dyes which are developed on the leather have become 
important for making black ooze, which requires a very- 
intense black. Other developed colors could be used when 
fullness is especially desired, but the process is long and 
tedious and does not give colors any taster to light than 
the basic dyes, which are applied much more simply. They 
are used at present only on chrome leather. The practice 
of diazotizing and developing seems to increase the soft- 
ness of the leather, wliich is particularly beneficial in 
making ooze. The process is carried out as cold as pos- 
sible with the exception of the dyeing at the beginning, so 
that the leather has small chance of being damaged. The 
following is a good formula for making black ooze calf 
skins with developed dyes: 

The chrome tanned calf skins are sorted for good flesh. 
They are then washed and neutralized, shaved, fat liquored 
for thirty minutes at 120° P. with 5% egg yolk and 10% 
flour, drained, hung up and dried, damped in sawdust, 
staked and buffed. The buffing must be done very clean 
so that they will not need to be buffed after dyeing. 

The percentages of dyes used in this formula are cal- 
culated on the dry weight. Wet the skins thoroughly at 
120° F, dye 30 minutes at 120° F., with 7% National Diazine 
Black H. G. Extra, dissolved in enough water to cover the 
skins. Add to dye bath 5% muriatic acid diluted with 
water at 90° F. Run 15 minutes, drain off and add 10% 
muriatic acid diluted with enough cold water to cover the 
skins and run 10 minutes. Add to the same bath 5% so- 
dium nitrate dissolved in cold water; run 15 minutes. 
Drain off and wash absolutely clean. Develop 15 minutes 
cold with 1% National Developer B D, 2% Soda Ash, dis- 
solved together in enough cold water to cover the skins, and 
drain off and rinse. Fat liquor 30 minutes at 120° F., with 
1% acid neatsfoot oil fat liquor. The skins are then dried 
on the hooks, damped in sawdust, staked, dry milled and 
tacked out. 

SULPHUR COLORS are dyestuffs which are soluble 
only in sodium sulphide or some other similar reducing 
agent. They have never found much use on chrome or 
vegetable tanned leather, because they have a tendency 
to make the leather tender. They have been recommended 
for dyeing oil tanned chamois leather. For this purpose 
equal parts of sulphur dye and sodium sulphide crystals 
are dissolved in boiling water. After the solution is cooled 
add one-tenth of formalin and one-fifth of soap. The 
chrome leather is dnmimed in this solution and then again 
fat liquored. These colors are very fast to washing. An- 
other use for sulphur dyes is for making grays on chrome 
tanned ooze calf skins. 

Colors produced by oxydation on the fibres are used 
tor fur dyeing. For this purpose two coal tar chemicals. 
Fur Black Superior and Fur Brown Base, are used. The 
tanned wool or fur skins are treated with a strong lime 
solution to remove grease and dirt and open up the hairs 
so that they will be prepared to absorb the mordants and 
dyes when they are applied. The lime is washed off and 
the wool or fur is mordanted. To insure a more rapid and 
intense absorption of the coloring matter developed in the 
dye bath, bichromate of potash sulphate or iron or copper 
in an acid or alkaline bath, are used for mordants and pro- 
duce different shades with the fur dyes. The furs are 
then squeezed and immersed in the dye solution and per- 
oxide of hydrogen, or sodium perborate, or peroxide neu- 
tralized with formic acid, is added. Various shades of 
brown, gray and black can be obtained; the process is car- 
ried out cold, so as to avoid damage to the skin. These 
colors have good fastness to light and washing. 



48 NATURE AND CONTROL OF TANNERY PROCESSES 



SIG. SAXE 

TANNING EXTRACTS 

SOLE SELLING AGENT 

ROBESON PROCESS CO. "SPRUCE" EXTRACT 

ROBERTS, EVANS & WOODHEAD .... "KHAKI CUTCH" EXTRACT 
iMniiQTRiAi rurMirai ro / "OSAGE ORANGE" EXTRACT 

INDUSTRIAL CHEMICAL CO. - - - |..heIVILOCK" AND "LARCH" EXTRACT 

200 FIFTH AVENUE, NEW YORK, U. S. A. 



■IlillllllllllillllilllllllllllilliilillililllllllllllllllllllilillllllillliW 

I Personal Service, NOT Routine Work | 



This organization extends to tanners that measure of co-operation 
which means an exact result in the finish of the leather. 

Due to our long experience in degreasing grains for patent and 
white leather production w^e have evolved a system which removes a 
sufficient amount of greases and oils from the skins, leaving them 
fit for the subsequent finishing processes. 

A trial lot of skins sent to us will be final proof of our ability to de- 
grease properly for the purpose. 



I WOBURN DEGREASING CO. | 

I WOBURN, MASS. HARRISON, N. J. 1 

llllllllllllllllllllllllllllllllllllllllllllllllllli 




BRACKETT- MASON -DODGE, Inc. 

Manufacturers of 

Dressings, Leather Stains and Finishes 

WHITE of every description for Shoe and Leather Manufacturers 

105 FOSTER STREET PEABODY. MASS. 



NATURE AND CONTROL OF TANNERY PROCESSES 



49) 



Dyestuffs for leather finishes must be selected to mix 
properly with the other materials in the finish. It is in 
the leather finishes that pigments are mostly used. The 
pigments are merely suspended in the finishes, but the 
dyestuffs are usually In solution, at at least they should be 
if they have been properly selected and dissolved. The 
pigments give a body of color to the finishes, while the 
dyes give the brightness required. The finishes contain, 
besides pigments and dyes, various mixtures of albumen, 
casein, gelatin, gums, seeds and moss, soaps, oils, waxes 
and shellac. When the finishes are dissolved in alkaline, 
aqueous solution, acid or direct colors must be used; when 
dissolved in alcohol, basic dyes or spirits soluble dyes must 
be used. Collodion varnishes require spirit soluble colors 
such as National Amyl Black or Acetyl Brown. 

In coloring the different kinds of leather for special 
purposes, if the best results are to be obtained the fol- 
long points should be observed: 

(1) Leather must be properly prepared to receive 
dyestuffs. 

(2) Dyestuffs must be selected which are best 
suited to the kinds of leather used and for the 
shade required. 

(3) The processes through which the leather 
must pass after dyeing must be chosen and 
arranged to cause the least possible injury 
to the color. 

(4) Great care must be taken with every process. 
Since the introduction of so-called pigment finishes, a 

great deal of carelessness has been shown in regard to the 
four above requirements. Pigments have covered a mul- 
titude of sins, but the connoisseur of fine leathers wants 
to see the characteristics of the grain of the leather. The 
result is that the best manufacturers are dyeing their 
leather with great care, so as to use only the smallest 
amount of pigment finish necessary. 

CHROME TANNED CAI^F SKINS are finished into 
several grades of fancy leather; the most important are 
the smooth and boarded grain colors and ooze leather in 
black and fancy colors. Tho skins are sorted after tan- 
ning. The grain colors are prepared for dyeing directly 
after tanning and whUe they are still wet. The ooze colors 
are washed and neutralized, fat liquored with 5% egg 
yolk and 10% flour, then dried out and bathed in the same 
way as described for black ooze. Fancy ooze colors can 
be made by bottoming with sumac or fustic extracts and 
fixing with sulphate of iron, tartar emetic or potassium 
titanium oxalate, then coloring with basic dyes or with 
acid or direct dyes and sometimes topping with basic dyes. 
Some light shades are made with pigments. Besides the 
developed black method for black ooze, a combination of 
logwood crystals and copperas. National Nigrosine 4523 
cone, and National Basic Table Black is used. 

Three of the most common colors on chrome tanned 
calfskins finished on the grain, can be obtained as follows: 



Chippendale 

Bottom 

20min. 110 °F. 

Fix 

10 min. 110°F. 

Dye 

20 min. 110 °F. 

Top Dye 



100 lbs. wet weight. 
3 lbs. Sumac ext. 
11/4 lbs. cutch. 
1% oz. potassium titanium oxalate. 

8 oz. National Resorcine Brown R. 



20 min. 110°F. 



Fat liquoi 
Gold Brown 

Bottom 
20 min. IICF. 
Fix 

10 min. 110°P. 
Dye 

20 min. 110°F. 
Top Dye 
20 min. 110°F. 
Fuc 

10 min. 110°F. 
Fat liquor 
Morocco 
Bottom 
20 min. 110°F. 
Fix 

10 min. 110°F. 
Dye 

20 min. 110°F. 
Top Dye 
20 min. 110°F. 



11 oz. National Bismarck Brown 53. 
14 oz. Victoria Green W. B. Crystals 

1 oz. Safranine A. 
ith acid fat liquor. 
urn lbs. wet weight. 
2 lbs. Sumac ext. 
11/2 lbs. cutch. 
1% oz. Potassium Titanium Oxalate. 



8 oz. National Resorcine Brown R. 
6 oz. National Chrysoidine Y ex. 
4 oz. National Phosphine W T. 

1% oz. Bichromate of Potash, 
rith acid fat liquor. 
100 lbs. wet weight. 
3 lbs. Sumac ext. 
1% lbs. Hypernic paste. 
1% oz. Bichromate of Potash. 

10 oz. National Acid Bordeaux. 

41/i oz. National Safi'anine A. 
7% oz. National Bismarck Brown 53. 
% oz. National Methyl Violet 2 B. Cone. 
Cry. 



CHROME TANNED GOATSKINS are mostly 
into black and colored glazed kid or patent kid. Black 
glazed kid or patent kid are colored as follows: 
Bottom 1% Logwood Crystals. 

20 min. 110°P. ys% Bicarbonate of Sodia. 
Fix 
lOmin. 110°F. %% Chloride of Iron. 

Drain off and dye 20 min. at 110° F. with 

%% National Nigrosine 27722 
or %% National Erie Black GXOO- 
and 1/16% National Methyl Violet 2B 
The glazed kid manufacturer is very firm in his con- 
viction that he must have a vegetable retannage on his 
skins in order to obtain a good glazed finish, but to make 
a full black with logwood and iron alone would give a 
harsh grain. 

CHROME' TANNED SIDE LEATHER is tanned the 
same as chrome tanned calf skin, but about one-third less 
dye is required because of the greater thickness of the 
side leather. 

VEGETABLE TAiWED SIDE LEATHERS are usually 
dyed with basic or acid dyes. The dyeing operations should: 
never be carried out at a temperature higher than 110° F. 
The sides should be cleared in sumac and tartar emetic. 

Light Tan Shade 

For 30 bark tanned hides— 750 sq. ft. 

Dye in a paddle wheel pit 20 min, at 110 F. with 
7% oz. National Resorcine Brown R 
1% oz. National Resorcine Brown RN 
14 oz. National Buffalo Black N B R 

Then add 3 oz. Sulphuric Acid and run 10 min. 

Dark Coffee Shade 

For 30 bark tanned sides — 750 sq. ft. 

Dye in a paddle wheel, put 60 min. at 110 F.. 

16 oz. National Bismarck Brown 53 



NATURE AND CONTROL OF TANNERY PROCESSES 



^■IIIIIIIIHIIIIIIIIII 





^1B>IRCL/IVST/-"40^42R4RKPL^ 




4'2 BY THE MOST PERFECT METHODS fsi 

WE H/IVE UPW/^RDS OF 200 DIFFERENT P/ITTERNS /IND C-flN FURNISH /INY NEW 
DESIGN ORGR>llN YOU nAV REQUIRE FOR SPECI/^L PURPOSES IN FUIT PLATES OR ROLLS 



m 



E. & F. KING & COMPANY, Inc. 

Boston, Mass. Salem, Mass. 

DEALERS IN TANNERS' CHEMICALS 




PRICES AND SAMPLES 
ON REQUEST 



Manufacturers of 
THE FOLLOWING SPECIALTIES FOR WHITE LEATHER 

BOLTED KING WHITE 

For Use in the Mill 

No. 2 BOLTED KING WHITE 

For Top Dressing 

WATERPROOFING WHITE 

For Waterproof Top Dressing 

LEATHER WHITE 

For Pearl and White Splits 

also 

PIGMENT AND DUST COLORS 

For Split and Buck Leather 
and 

CASTOR AND LINSEED OIL COLORS 



NATURE AND CONTROL OF TANNERY PROCESSES 



51 



6 oz. National Safranine A 

1 oz. National Metliylene Blue B B 

1 pint Acetic Acid 

Then fix 15 minutes with 6 oz. Bichromate 

of soda 
When dyeing bark tanned side leather on a brushing 
machine or on a table, acid dyes give the most satisfac- 
tory results. 

BROAVN GLAZED KID is most successfully made with 
acid dyes on a vegetable bottom. The skins are first care- 
fully washed and neutralized. 

For 100 lbs. wet shaved weight 

Bottom 20 min. at 110 F. with 

IVa lbs. Fustic Ext. 

2 oz. Logwood Cry. 
Fix 15 min. at 110 P. 
1% oz. Chloride of Iron 

Drain off and dye 30 min. at 110 F. 

4V^ oz. National Resorcine Brown R 

41/2 oz. National Leather Mahogany C M Y 

2 oz. National Fast Acid Red T K C 

2 oz. National Induline N T 

Drain and wash. Fat liquor with 4% Acid 

Pat liquor 

Mahogany Glazed Kid 

For 100 lbs. wet shaved weight 

Bottom 20 minutes at 110 F. with 1% lbs. 

Sumac ext. 

% Ins, Hypernic paste 

Fix 15 minutes at 110 F. 

2 oz. Bichromate of Potash 

Drain oft and dye 30 minutes at 110 F. 

16 oz. National Mahogany Brown BL 

2 oz. National Fast Red S. Cone. 

2 oz. National Induline N T 
Drain off, wash, fat liquor with 4% Acid tat liquor. 
Vegetable Tanned Sheepskins and Goatskins are dyed 
with acid or basic dyes. The principal difference in treat- 
ing the different kinds of vegetable tanned leathers is 
made in the method o£ preparation for coloring. The 
dyeing operations should be carried out at about 110 F. 

India tanned sheep and goat skins contain consider- 
able grease as well as vegetable tanning material. The 
grease must be removed from the surface of the leather 
before it can be dyed a clear even color. This is done by 
washing the skins first in soda to free the grease, then 
retanning with sumac, then clearing with sulphuric acid, 
then finally the skins are rinsed with plenty of water. 
The skins to be colored black on the grain leaving the 
black white, are stained on the grain by brushing with 



8 oz. National Basic Table Black, 2 oz. Acetic acid and 2 
quarts gum Tragacanth solution to one pail of water. 

Pickled slieepskins tanned in sumac, are simply cleared 
with sulphuric acid and rinsed in water. Pickled sheep- 
skins tanned in quebracho, for fancy colors, are washed up 
in sumac, which is then fixed with tartar emetic. 

India sheep skins and pickled sheep skins are colored 
similarly and can be considered together. Whenever good 
fastness to washing is required, the skins should be dyed 
with basic dyes and the color set with bichromate of 
potash. On very light shades which must be slightly 
saddened, bichromate of potash must be used intead of 
blue or green, when possible. When full shades are made 
with acid dyes, such as bright reds, dyed with National 
Croceine Scarlet MOO, about 2 quarts of formic acid to 30 
dozen skins should be added toward the end of the dyeing 
operation. Formic acid is generally chosen because it is 
quite as strong as sulphuric acid and will evaporate while 
sulphuric acid is stable. Dyes for ooze leather should be 
selected for their penetrating qualities. The best acid 
dyes for this purpose are National Wool Yellow Ex. con. 
Wool orange A Cone. Croceine Scarlet MOO add Induline 
N T, the best penetrating basic dyes are National Aura- 
mine O, Chrysoidine Y Ex. and 3 R, F^ichsine N. B. Cry. 
Methyl Violet 2 B cry. 

Coffee Brown 

30 dozen Quebracho tanned sheepskins 85 

ft. per dozen 
Dye 20 min. at 110 F. 

6 oz. National Wool Orange A Cone. 
12 oz. National Fast Brown BN 

Dye 20 min. at 110 F. 

42 oz. National Phosphine W T 

34 oz. National Bismarck Brown 53 

7 oz. National Methylene Blue BB 
Fix 15 min. 110 F. 

2 lbs. Bichromate of Potash 
12 oz. Blue Stone. 

Tan 
30 doz. Quebracho tanned sheepskins 85 

ft. per dozen 
Dye 20 min. at 110 P 
24 oz. National Wool Orange A Cone. 
12 oz. National Resorcine Brown R 
Dye 20 minutes at 110 F 
72 oz. National Phosphine W T 
1% oz. National Methylene Blue BB 
Fix 15 min, 110 F. 
2 11>6. Bichromate of Potash 



Chrome Tanned White Leather 



In addition to the usual process for making white 
leather, namely, by the use of alum and formaldehyde, 
chrome tanned white leather is commercially produced ac- 
cording to one of the following methods: namely, 

(1) For "soft" white leather (i. e., lining splits): 
Use of the ordinary two-bath process with an ex- 
cess of acid and sodium thiosulfate in order to 
effect the maximum deposition of sulfur within 
the goods. The sulfur so deposited renders the 
resulting leather very light in color. 

(2) For "firm" white leather: Use of a one-bath 
bisulfite chrome-liquor, followed by treatment 
with acid and sodium thiosulfate. In this process 
the deposited sulfur again acts as a "bleaching" 



agent. The leather is rendered perfectly white 
by the application of whiting (magnesium car- 
bonate). 
(3) By a combination of the onebath process and of 
the alum-formaldehyde process. The goods are 
first run in the chrome-liquor until "struck 
through," when they are neutralized with borax 
and entered into an alum-liquor containing alum, 
salt and flour. After being drummed In this 
liquor until tanned, the leather is treated with 
formaldehyde, and subsequently fat-liquored in 
an emulsion of starch, egg-yolk and sulfonated 
neatsfoot oil. 
The processes outlined above are typical of those em- 
ployed by well-known tanning concerns in this country. 



NATURE AND CONTROL OF TANNERY PROCESSES 



READY 
FOR 
YOU! 




As the edition is limited you will have 
to act quickly to receive your copy. 



PRICE $3.00 PER COPY 



Shoe and Leather Reporter Co. 



166 ESSEX STREET 



BOSTON, MASS. 



Alphabetical Index to 
Advertisers 



American Dyewood Co 46 

Arbib & Houlberg 16 

Baker, G. W., Machine Co 16 

Bill, E. H. & Co 16 

Brisk, J. & Co 9 

Brackett-Mason-Dodge, Inc 48 

Cassidy, E. P. & Co 19 

Chemical Research Co 40 

Commonwealth Oil Co 42 

Damon, Fred W 42 

Dnrrnn Trading Co., Ltd 13 

li.niii-, Martin Co 26 

]>,..vi\uv^,-v. 1 13 

D.^liiir, Criram & Co., Inc 13 

Du Pont, E. I. de Nemours & Co., Inc 18 

Faraone, Frederick & Co 16 

Fearon, Brown Co 13 

Harkin, Wm. & Sons 22 

Hauthaway, C. L. & Sons, Inc 20 

Heymann, Albert & Co 21 

Horwitz & Arbib. Inc 14 

International Products Co 28 

Johnstone, W. W 13 

King, E. & F. & Co., Inc 50 

Kossman, Anthony R 13 

Lapham, Walter S 21 

Larkin, D. J. Co 40 

Louisville Cement Co 14 

Lovejoy, D. & Son 20 

Marden-Wild Corp 8 

Montgomery, W. L. & Co 16 

National Aniline & Chemical Co., Inc 44 

National Oil Products Co 56 

New York Color & Chemical Co 2 

Oil & Chemical Corp 40 

Persson & Co 16 

Poll. Victor J. & Co 40 

Quebracho Products Co., Inc 12 

Ringler, F. A. Co 50 

Rockland & Rockport Lime Corp 14 

Salem Oil & Grease Co 36 

Saxe, Sis 48 

Schmoll, Armand, Inc 10 

Schmoll, Fils & Co., Inc 1 

Seccomb-Kehew-Bradley Co 38 

Shaw, John & Co 38 

Sheridan, T. W. & C. B. Co 24 

Solvay Process Co 32 

Spencer, C. A. cfe Son Co 34 

Star, Jules & Co 4 

Stehling, Charles H. Co 10 

Sternteld, Weil & Co 13 

Tannin, The Corp 6 

Tauber, Frederick 13 

Traud, Alexander & Sons 32 

Tupman, Thurlow Co., Inc 10 

Turner Tanning Machinery Co 55 

United States Brokerage Co 19 

Whitney Machine Co 54 

Whittemore-Woodbury Co 36 

Wing & Evans, Inc 32 

Woburn Degreasing Co 48 

Woburn Machine Co 53 



NATURE AND CONTROL OF TANNERY PROCESSES 



THE NEW 

Superior Splitting Machine 




I. B. WILLIA-MS & SONS 
Dover, N. H. 

March 20, 1022. 
Woburn Machine Company 
Woburn. Mass. 
Gentlemen : The Superior Splitting 
Machine which you iustalled here is 
giving complete satisfaction and we are 
very glad to recommend it most highly. 
As far as we know. It is the best ma- 
chine of its Ivind in the marlvet. 

Its major superior points seem to be 
In more rigid and better construction, 
much more convenient and perfect ad- 
justments and a much more scientific 
Installation on tlie grinding equipment 
making it possible to obtain a very 
much better edge. We are using this 
machine on dry work and are getting 
excellent results, far more satisfactory 
than with our old machines. We have 
no doubt whatever but that it would be 
equally superior for wet work, if we 
happened to need it for this class of 
splitting. We find as stated above, we 
can get better edge and do not have the 
difficulty of its turning in the hard 
stock which we experienced with the 
other machines. 

We would particularly like to stress 
the point of its excellent construction, 
and fine workmanship put into its 
building. 

Very truly yours. 
P. C. B. I. B. WILLIAMS & SONS. 



This New Improved Splitting 
Machine has a heavier frame 
than any other built. Its con- 
struction tbruout is of the 
same sturdy proportions, made 
to work readily, steadily, con- 
serving time and labor charges. 

Every part is easily accessible to 
workmen. 

It is the one machine that docs 
the job efficiently at low pro- 
duction costs. 



March 24, 1922. 



Gentlemen : The Superior Splitting 
Machine which you installed here has 
given us perfect satisfaction. It has a 
good many advantages over the old 
Splitting Machine in the adjustments. 
One especially, is In changing tlie knife, 
great advantage over the 



old 



For Further Particulars write to the Manufacturers — 

Woburn Machine Company 

WOBURN, MASS., U. S. A. 



NATURE AND CONTROL OF TANNERY PROCESSES 

7^his IS a perfect TaAe - ©fK 
oFa ^AtKEFL HIDE / 




Fleshiwgi^mmnes insure 

G> E FtFE^T^c^PfLESH I NG 



^^«Iiiiiroiiiiniaiin<*"^«^ 



IMPROVED 

MODEL "M" 

FLESHING MACHINE 



XI 




%J 

AGENTS 

W. & C. PAN TIN 

Ijon(3on 
G. B. MARIO SPIGNO 
Genoa 



NATURE AND CONTROL OF TANNERY PROCESSES 




Turner No. 20 Beam House Machine 



The Turner Tanning Machine G>mpany offers a greater variety of 
Beam House Machines than all other Manufacturers combined, rang- 
ing in size from 24 inches to 1 26 inches, and handling anything from 
a rat skin to the largest hide. 

The illustration above is only one of this extensive line, this type being 
recommended for calf, sides, and horse. 

An Automatic Grinder supplied with all No. 20 Machines increases 
its value very materially, and is a distinct feature of this type. 

The Turner Tanning Machinery Company 

MAIN OFFICE AND WOBKS: 

PEABODY, MASS., U. S. A. 



NEWARK, NEW JEKSET 



MILWAUKEE, WISCONSIN 



LEEDS, ENGLAND 



PARIS, FRANCE 



NATURE AND CONTROL OF TANNERY PROCESSES 



Sulphonated Oils Spon|[ing Compound 




Products 



Moellon Degras 



Fig Soapt 



NATIONAL OE. PRODUCTS CO. 

HARRISON, N. J. 

pLAjrrs 

HARRISON, n. J. CHICAGO, ILL. 

ST. JOHNS, N. F. 

WAREHOUSES 

MBLWAUUE;! GLOVEBLSVflXI 70tONTO SAN FR.\RaSCO PEARODY QIMBEC 






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